ListformBusyBox
Calculator (recommend?)
If the basic built-in calculator isn't advanced enough for your needs and you have experience with graphing calculators, I'd recommend Graph 89.
https://github.com/milaq/graph89
Note that you have to go to the Texas Instruments website (on a desktop machine, weirdly they don't like letting you download on mobile) and download the ROM of your favorite graphing calculator. Load it into the app, and then you have an awesome little graphing calculator app.
SMS messaging
In my experience SMS is unreliable in secondary profiles. I tried it at first back in 2023 and then quickly gave up. If you rely on getting SMS messages in a timely way without some being dropped, you need to be in the Owner profile.
Could be different now in 2025, I don't know. Worth giving it a shot if you have the patience to experiment.
Brave Browser (Firefox? Should I install a non-privacy-related browser here?)
About Brave vs Firefox, see here:
https://discuss.grapheneos.org/d/20618-brave-browser/17
Elsewhere on the forum, GOS mods and devs tend to recommend Vanadium for best security and Brave for better fingerprinting resistance (privacy).
OSMAnd or Organic Maps (which is more privacy-focused?)
Both are pretty good with privacy IMO. I find Organic Maps to have better usability. Try them both, see what you like.
Social Media
Evil companies, social harm at scale (just my opinion though, ha, no judgement)
If you must have them, maybe you could get away with just lurking using alternative frontends to enjoy more privacy. A handy list is here:
https://libredirect.github.io/
You can also use LinkSheet to automatically change links from normal social media to alt frontends
https://github.com/LinkSheet/LinkSheet
Strava
Gnarly app, gets implicated in a breach of sensitive location data every few years. Might be an easy one to replace with something more privacy respecting, if interested:
https://discuss.grapheneos.org/d/16966-fitness-app-was-used-to-locate-the-worlds-most-powerful-people
Aside from apps, agreed with others to start easy/simple and ratchet up gradually as you adjust. Important to remember that burnout is also a threat.
Congratulations on the big move, GOS is life-changing and awesome, best of luck!