So, I'm not familiar with the Shizuku/Canta method, but would it be possible to install microG [F-droid repo] to spoof the presence of Google Play?

Is there a way you can install Google Play as a user app? Maybe in a second profile? Just a matter of switching to the second profile when you want to check your schedule.

If a second profile isn't an option, GP could be disabled until you need it.

I can't say what's involved in doing this but it must be possible as GrapheneOS does this.

Use websites whenever possible instead of apps. And try your best to use FOSS apps from places like FDroid as much as possible.

Google Play Services or Store? If it's Services, you could make an exception and keep it, because many third party apps need it to work. I kept it and removed all the other Google apps. So they get no ad revenue from me.

Find alternatives to the ones that require play. See if they host their apk on their site or on other storefronts.

I dropped the Mistral AI because it required google, and also it was shit.