The key point to know is that this app has a huge footprint: 7.54 GBs.  In addition to Revit LT 2021, another 18 dependent apps are installed, mostly various image libraries.  The total install took about 45 minutes on my test machines, but up to 2 or 3 hours on some user's machines.

Install:

• RevitLT_2021_r1_G1_Win_64bit_dlm\setup.exe /t /qb /w /language en-us /c RLT: INSTALLDIR="%ProgramFiles%\Autodesk\Revit LT 2021" ADLM_EULA_COUNTRY=US InstallLevel=5

Hotfix install (if necessary):

• RevitLT_2021_1_2.exe /install /passive /norestart /log "C:\My\Logfile\Location\Autodesk Revit LT 2021.1.2 hotfix.log"

Uninstall:

Is a lot more "fun".  I put all the uninstallers into a Powershell script that uninstalls everything from smallest to largest app.  Note the comment at the end: Autodesk Genuine Service will not allow itself to be uninstalled, and if forced, any other Autodesk product will stop working.

# Uninstall all Autodesk Revit LT 2021

$logpath = '"C:\My\Logfile\Location\Logs\' # not a mistake; the leading double-quote needs to be part of the string

# Per Autodesk, uninstall peripheral programs first, from smallest to largest

#Uninstall Personal Accelerator for Revit
$MSIarguments =
    @(
    "/X"
    "{E014CF6D-8F81-4A46-9A43-3CE872C2231B}"
    "/qb-!"
    "/L*v"
    $logpath + 'Autodesk Personal Accelerator for Revit Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Advanced Material Library Base Resolution Image Library 2021
$MSIarguments =
    @(
    "/X"
    "{C9FDA270-A0B9-45EE-8748-F37DF1370767}"
    "/qb-!"
    "/L*v"
    $logpath + 'Autodesk Advanced Material Library Base Resolution Image Library 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Revit Unit Schemas 2021
$MSIarguments =
    @(
    "/X"
    "{CDCC6F31-2021-4901-8E9B-D562B70697B6}"
    "/qb-!"
    "/L*v"
    $logpath + 'Autodesk Revit Unit Schemas 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Advanced Material Library Low Resolution Image Library 2021
$MSIarguments =
    @(
    "/X"
    "{AB7DC10F-1D72-4F90-988F-CDC2D6323A48}"
    "/qb-!"
    "/L*v"
    $logpath + 'Autodesk Advanced Material Library Low Resolution Image Library 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Material Library Base Resolution Image Library 2021
$MSIarguments =
    @(
    "/X"
    "{EFC36459-CD89-44F3-BA04-B7C5804199AF}"
    "/qb-!"
    "/L*v"
    $logpath + 'Autodesk Material Library Base Resolution Image Library 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Single Sign On Component
$MSIarguments =
    @(
    "/X"
    "{951BB060-1350-4C93-BD83-D966C51D4005}"
    "/qb-!"
    "/L*v"
    $logpath + 'Autodesk Single Sign On Component Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Material Library 2021
$MSIarguments =
    @(
    "/X"
    "{8C559572-4A10-43C2-9346-6E7C7E012487}"
    "/qb-!"
    "/L*v"
    $logpath + 'Autodesk Material Library 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Material Library Low Resolution Image Library 2021
$MSIarguments =
    @(
    "/X"
    "{AD6312B6-3056-460A-833F-02654FAC5FCE}"
    "/qb-!"
    "/L*v"
    $logpath + 'Autodesk Material Library Low Resolution Image Library 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Material Library Medium Resolution Image Library 2021
$MSIarguments =
    @(
    "/X"
    "{69D8FFED-B14E-4998-BBC2-535006E195D6}"
    "/qb-!"
    "/L*v+"
    $logpath + 'Autodesk Material Library Medium Resolution Image Library 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Advanced Material Library Medium Resolution Image Library 2021
$MSIarguments =
    @(
    "/X"
    "{B4545986-9002-4090-9E58-44F985F2FF4F}"
    "/qb-!"
    "/L*v+"
    $logpath + 'Autodesk Advanced Material Library Medium Resolution Image Library 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Cloud Models for Revit 2021
$MSIarguments =
    @(
    "/X"
    "{BB495CF5-2101-0030-0000-97E7D7D021A1}"
    "/qb-!"
    "/L*v+"
    $logpath + 'Autodesk Cloud Models for Revit 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Cloud Models for Revit 2021
$MSIarguments =
    @(
    "/X"
    "{CDCC6F31-2021-4912-8E9B-D562B70697B6}"
    "/qb-!"
    "/L*v+"
    $logpath + 'Autodesk Cloud Models for Revit 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Cloud Models for Revit 2021
$MSIarguments =
    @(
    "/X"
    "{BB495CF5-2101-0020-0000-97E7D7D021A0}"
    "/qb-!"
    "/L*v+"
    $logpath + 'Autodesk Cloud Models for Revit 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Revit Content Core-RLT 2021
$MSIarguments =
    @(
    "/X"
    "{36E70770-2021-0410-0000-56DE2DECF483}"
    "/qb-!"
    "/L*v+"
    $logpath + 'Autodesk Revit Content Core-RLT 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Autodesk Revit Content Core 2021
$MSIarguments =
    @(
    "/X"
    "{583895D0-2021-0410-0000-9241AD002DA5}"
    "/qb-!"
    "/L*v+"
    $logpath + 'Autodesk Revit Content Core 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Cloud Models for Revit 2021
$MSIarguments =
    @(
    "/X"
    "{BB495CF5-2101-0020-0000-97E7D7D021A0}"
    "/qb-!"
    "/L*v+"
    $logpath + 'Autodesk Cloud Models for Revit 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Uninstall Revit 2021
$MSIarguments =
    @(
    "/X"
    "{7346B4A0-2100-0410-0000-705C0D862004}"
    "/qb-!"
    "/L*v+"
    $logpath + 'Autodesk Revit 2021 Uninstall.log"'
    )
Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait

#Stop running Autodesk
Stop-Process -Name AutodeskDesktopApp -Force -ErrorAction SilentlyContinue
Stop-Service -Name AdAppMgrSvc -Force -ErrorAction SilentlyContinue

#Uninstall Autodesk Desktop App
cmd.exe --% /c "C:\Program Files (x86)\Autodesk\Autodesk Desktop App\removeAdAppMgr.exe" --mode unattended

#Delete C:\Program Files\Autodesk\Revit LT 2021 if it exists
$path64 = "C:\Program Files\Autodesk\Revit LT 2021"
If(Test-Path $path64) {Remove-Item -Path $path64 -Recurse -Force}

#Delete all of C:\Program File\Autodesk if it is empty (do this separately in case there are other Autodesk apps in this folder)
$pathAutodesk64 = "C:\Program Files\Autodesk"
If(Test-Path $pathAutodesk64)
    {
        # Check if empty
        $directoryInfo64 = Get-ChildItem $pathAutodesk64 | Measure-Object
        $directoryInfo64.Count
        If($directoryInfo64.Count -eq 0) {Remove-Item -Path $pathAutodesk64 -Recurse -Force}
    }

#Delete C:\Program Files (x86)\Autodesk\Autodesk Desktop App if necessary
$path86DesktopApp = "C:\Program Files (x86)\Autodesk\Autodesk Desktop App"
If(Test-Path $path86DesktopApp) {Remove-Item -Path $path86DesktopApp -Recurse}

#Wait for \Autodesk Desktop App to finish deleting
Start-Sleep -Seconds 1

#Delete C:\Program Files (x86)\Autodesk if it exists and is empty
$path86 = "C:\Program Files (x86)\Autodesk"
If(Test-Path $path86) # if it even exists
    {
        # Check if empty
        $autodesk86 = "C:\Program Files (x86)\Autodesk"
        $directoryInfo86 = Get-ChildItem $autodesk86 | Measure-Object
        $directoryInfo86.Count
        If($directoryInfo86.Count -eq 0) {Remove-Item -Path $path86 -Recurse}
    }

#Delete C:\Windows\System32\config\systemprofile\AppData\Local\Autodesk\Autodesk Desktop App if it exists
$Local86 = 'C:\Windows\System32\config\systemprofile\AppData\Local\Autodesk\Autodesk Desktop App'
If(Test-Path $Local86) {Remove-Item -Path $Local86 -Recurse}

#Delete C:\Windows\SysWOW64\config\systemprofile\AppData\Local\Autodesk\Autodesk Desktop App if it exists
$Local64 = 'C:\Windows\SysWOW64\config\systemprofile\AppData\Local\Autodesk\Autodesk Desktop App'
If(Test-Path $Local64) {Remove-Item -Path $Local64 -Recurse}

#Delete C:\Windows\System32\config\systemprofile\AppData\Roaming\Autodesk\Autodesk Desktop App if it exists
$Roaming86 = 'C:\Windows\SysWOW64\config\systemprofile\AppData\Roaming\Autodesk\Autodesk Desktop App'
If(Test-Path $Roaming86) {Remove-Item -Path $Roaming86 -Recurse}

#Delete C:\Windows\SysWOW64\config\systemprofile\AppData\Roaming\Autodesk\Autodesk Desktop App if it exists
$Roaming64 = 'C:\Windows\SysWOW64\config\systemprofile\AppData\Roaming\Autodesk\Autodesk Desktop App'
If(Test-Path $Roaming64) {Remove-Item -Path $Roaming64 -Recurse}

#Uninstall hotfix 2021.1.1
.\64\RevitLT_2021_1_2.exe /uninstall /passive /norestart /log "C:\My\Logfile\Location\Logs\Autodesk Revit LT 2021.1.2 Hotfix Uninstall.log"
   
#Uninstall Autodesk Genuine Service
<#
    Notes
        Cannot be removed if any Autodesk product is still installed
        If all Autodesk products have been removed, Genuine Service will remove itself after 24 hours or 2 weeks (sources disagree) but will not allow itself to be removed
        Workaround (tested and confirmed): delete "C:\ProgramData\Autodesk\Adlm\ProductInformation.pit" and "C:\Users\username\AppData\Local\Autodesk\Genuine Autodesk Service\id.dat"
        Not uninstalling because there may be other Autodesk products on a user's computer.
        For future reference:
       
    $MSIarguments =
        @(
        "/X"
        "{54A00624-3EF9-49A2-92A9-7244EADD0212}"
        "/qb-!"
        "/L*v+"
        $logfile
        )
    Start-Process "msiexec.exe" -ArgumentList $MSIarguments -Wait
#>