Android

Honestly, I was surprised at the lack of compatability issues. It had less issues than any custom ROM I've used, and I've used a LOT of custom ROMS over the years.

I had to toggle off the anti exploit hardening for a few apps, but I eventually just ditched those apps and replaced them with their respective websites or with FOSS equiviliants.

Flashing the ROM was easier than my older Android phones too.

Google Wallet (or whatever they call it these days) doesn't work, even if you install Google Play Services. So NFC payments are simply not possible for me. I've heard that some banks have NFC payments built into their apps, but I have never seen a list. I'd switch banks if it meant I could get this to work.

There's currently no NLP (network location provider) support, so if you don't have an actual GPS satellite signal, you will not have active location unless you use Google's location services. There's been some talk of including a new NLP service in the future but I don't know of any timeline.

Even when using Google Location Services, accuracy is worse than on the stock Pixel OS. I'm not sure why, but I get tons of drift indoors (whether Wi-Fi is enabled or not), whereas on PixelOS it was almost always stable. It also means navigation apps will sometimes think I magically hopped off a bridge and onto the side street below or something like that.

There's no "extreme battery saver" mode like on Google's Pixel OS. When I switched, I didn't realize that was a Google feature rather than an Android/AOSP feature.

If you rely on Google backups for app data, I'm not sure if there's any reasonable way to get that into GOS since it can only happen during initial setup. Might be solutions to this, but personally I didn't spend time on it because there was nothing I cared too much about. Check your apps to see if they have settings import/export functions. A lot of open-source apps (like Lemmy clients) do.

GOS has an open-source backup system called Seedvault, but of course if you ever want to switch back to a stock Android OS, you won't be able to bring those backups with you since apps simply can't get that level of access on any stock Android OS. You're stuck on GOS or other third-party OSes that support Seedvault, or maybe rooting if that's possible.

If you use WhatsApp (ew), be aware that it only supports backup via Google Drive. And you can't manually download and restore that backup without adding Google Play Services and logging in.

Lawnchair and other third-party home screens seem to work worse on GOS than stock Pixel OS when it comes to the app switcher animation bug. I've seen some GOS forum threads about this so I know I'm not alone.

If you want your sms/mms, back them up.

Graphene is only for Pixel phones. That's been enough to stop me from pursuing it.

Some banking and similar apps don't work, or have some features nonfunctional (like NFC). You can always use the website and carry a card like we did in 2012.

You'll lose all your local data as the bootloader gets unlocked, so back them up.

Tutorials on modding phones, from my experience, are fairly obtuse despite the process itself usually being rather simple and straight forward.

If you want to go as privacy-oriented as possible, you'll likely pick a vanilla system (that is, as close to AOSP, "Android Open Source Project"), and will often be on the lookout for software that is either DRM-free (no dependency on 3rd party software), or open source / FOSS ("Free and Open Source Software"). Also VPNs to mask your online usage may come with their own set of cobsiderations, like some sites breaking, some others considering it ban-worth, and others setting prices, languages, etc., to a given region.