Uninstall instructions could help more

I have a system that had Sophos Endpoint installed when it was running on an Intel Mac. It was then migrated to Apple Silicon (M1), and then (following difficulties that I thought might have been related to Sophos) Sophos was uninstalled using the Uninstaller. So far so good.

Now I want to install it again. Attached is the error I get: ("Your system already has the Sophos Endpoint Installed"). I guess the migration has put something somewhere that the uninstaller didn't or couldn't remove. There's an engineering issue there, but also a documentation one perhaps: I might follow your directions to uninstall but I have no uninstaller. Your directions at https://docs.sophos.com/esg/endpoint/help/en-us/help/Uninstall/index.html could usefully say something about what to do if it doesn't work, or isn't there.