@rnphil I think the issue is that you have installed Freescout with Cloudron user management. Because of this, it takes ownership of the OIDC provider settings and reconfigures the OIDC provider . If you go to Location section of FreeScout, I guess it says "Cloudron User management" (instead of "Dashboard visibility".)
You can try this:
take a backup of your current freescout and download the backup configuration file (it's a button to the right of the backup).
make a new installation of freescout alongside the existing one. when you install , make sure to select "Let the app manage it's own users"
Then, app -> backup -> import . put the backup configuration file from step 1
I think that should sort it out. If everything works, just move your existing install to some other domain and move the new one to the correct location .