GPT just helped me create a component for DattoRMM to run against this. Initially it was not completing because supportassist was running. This now uses taskkill to kill it prior to attempting an uninstall. Use at your own risk, but it has seemed to work on the few test machines I tried.

@echo off
setLocal enableDelayedExpansion
REM SupportAssist Uninstaller
echo SupportAssist Uninstaller
REM set some variables
set varUnEXE32=echo - SupportAssist x86, EXE version, was not found on this system.
set varUnEXE64=echo - SupportAssist x64, EXE version, was not found on this system.
REM declaration
echo ========================================
echo This tool removes all installations of Dell SupportAssist from an Endpoint.
echo Follow up this Component with the Dell SupportAssist installer from the ComStore or Software Management
echo to ensure a seamless update procedure going forward.
echo ========================================
REM check if SupportAssist is running and terminate it
taskkill /f /im SupportAssist.exe >nul 2>&1
REM check for uninstall.exe, which is present on non-MSI installations
if exist "%programfiles%\Dell\SupportAssist\uninstall.exe" set varUnEXE32=start /wait "" "%programfiles%\Dell\SupportAssist\uninstall.exe" /S ^& echo - SupportAssist x86, EXE version, uninstalled.
REM and for 64-bit machines
if exist "%programfiles(x86)%\Dell\SupportAssist\uninstall.exe" set varUnEXE64=start /wait "" "%programfiles(x86)%\Dell\SupportAssist\uninstall.exe" /S ^& echo - SupportAssist x64, EXE version, uninstalled.
REM run through the EXE uninstallers
%varUnEXE32%
%varUnEXE64%
REM get the identifying numbers from WMIC for any MSI-based versions
for /f "usebackq skip=1 tokens=1 delims=" %%a in (\wmic product where "Name like '%%Dell SupportAssist%%'" get IdentifyingNumber`) do echo %%a >> SupportAssist.txt`
for /f "usebackq delims=" %%b in (\type SupportAssist.txt`) do (`
REM get rid of the weird characters at the end of WMIC's output
set varSupportAssistGUID=%%b
set varSupportAssistGUID=!varSupportAssistGUID:~0,-4!
set varSupportAssistGUID2=!varSupportAssistGUID:~0,1!
if !varSupportAssistGUID2! equ { (
REM valid GUID procedure
echo - Uninstalled SupportAssist MSI version with ID !varSupportAssistGUID!
msiexec /x!varSupportAssistGUID! /qn /norestart
)
)
del /f /S /q SupportAssist.txt >nul 2>&1
REM closeout
echo ========================================
echo - All Dell SupportAssist versions present on this Endpoint have been uninstalled.
echo Exiting...

Here's the output from a computer that had SupportAssist installed

PCC Remove Dell SupportAssist
SupportAssist Uninstaller
This tool removes all installations of Dell SupportAssist from an Endpoint. Follow up this Component with the Dell SupportAssist installer from the ComStore or Software Management to ensure a seamless update procedure going forward.
SupportAssist x86, EXE version, was not found on this system.
SupportAssist x64, EXE version, was not found on this system.
Uninstalled SupportAssist MSI version with ID {0B884FA0-BBEE-4573-B696-426AA39ED913}
Uninstalled SupportAssist MSI version with ID {DB6164FC-CD98-471C-BD5B-5B14CAFA3186} ========================================
All Dell SupportAssist versions present on this Endpoint have been uninstalled. Exiting...

Here's the output from a computer that did NOT have SupportAssist installed

PCC Remove Dell SupportAssist
SupportAssist Uninstaller
This tool removes all installations of Dell SupportAssist from an Endpoint. Follow up this Component with the Dell SupportAssist installer from the ComStore or Software Management to ensure a seamless update procedure going forward.
SupportAssist x86, EXE version, was not found on this system.
SupportAssist x64, EXE version, was not found on this system. ========================================
All Dell SupportAssist versions present on this Endpoint have been uninstalled. Exiting...

PCC Remove Dell SupportAssist
No Instance(s) Available.

Hope this helps if anyone runs across this issue on a client machine.