Have found a process to uninstall old version.

Used the Microsoft
"Fix problems that block programs from being installed or removed"
At "Fix problems that block programs from being installed or removed (microsoft.com)"

Then installed latest version of Dell SupportAssist.

There is a Powershell script distributed with the deployment package - have you tried that to remove SA?

It is called SupportAssistUninstall_Cleanup.ps1

Way I deleted the slopware:

1. Go to C:\Program Files\Dell

2. Attempt to delete the SupportAssist file (and SARemediation if you want, both are broken bloatware that break your computer for no benefit.)

3. When it says its "open in another program" do the following -

1. Open resource monitor (Windows +R to open Run then type Resmon.exe)
2. Open the CPU tab in the monitor
3. Expand "associated handles"
4. Search for "supportassist"
5. End every process that has it open with the name