Have you migrated your user from one domain to a new domain?
if So you can move your user from one domain to another domain.
You can use the below command to fix your problem
$user = Get-SPUser -Identity "DomainA\JaneDoe" -Web https://webUrl
Move-SPUser -Identity $user -NewAlias "DomainB\JaneDoe"
For more details please use below URL
The assembly you added seems to be "Microsoft.Office.Server.WorkManagement.UI" not "Microsoft.Office.Server.Search.Internal.UI.SearchResultsLayoutPage" shown in the error message.
How about adding the following assembly name space to web.config instead?:
Hope it works!
You can remove the servers (except WFE) from the farm by running the Configuration Wizard/using PowerShell/using Central Administration, and then uninstall SharePoint product from each server.
Or you can just remove the servers by uninstall SharePoint directly using Control Panel.
However, uninstalling SharePoint product does not really “clean” the farm/...
If you run the config wizard on the WFE that is hosting Central Admin, you will have to option to remove Central Admin from the server in the wizard. Then all you need to do is run the wizard on the APP server and have it host the central admin site.
On a side note I would not recommend using SP2016 for a new farm, I'd strongly recommend SP2019. SP2016 ...