halfyear includes people trying out different instances; monthly shows just the one(s) they settled on

That seems almost exactly what the sudoers file is meant for.

If several actions have to happen at once (call the phone first), or need parameters, or need a kill switch, that is what a script with the SETUID bit does.

After choosing, it’s just “sign up, install one of the apps and sign in again, start reading or subscribing” - so not a world of difference from someone who has just that e.g. Threads or Reddit or a certain discord is ‘their community’?