thure
Sorry, but there must be a typo, because otherwise I can't see the problem with 30 minutes screen time …
The screen cannot turn off after one minute, when you have set it to 30 minutes, right?
Sometimes, in some apps the screen locks and turns off really later as wished – but it works.
I have set it to 30 seconds. And I use the app BatteryBot Pro, which is an older app, but I don't know a newer really serious working battery monitor, therefore I use this app and it is one of a few apps, where screen locking sometimes not works within 30 seconds, but within a few minutes. No problem, because it needs very few energy, but it happens.
But maybe it's just a random error with this app and it's the same error as with the brightness control, which still doesn't work properly (not a GrapheneOS error, but an Android error!).