But AOSP already is “Android without proprietary Google code”, simply because “Android” means AOSP + Google Play Services + compatibility certification. It’s getting increasingly more and more barebones as Google moves functionality into Google Play Services, but it is what the vast majority of third party ROMs are based on.
How they manage to then improve compatibility differs. Truly ungoogled ROMs just don’t - either the app works with AOSP, or it’s not welcome on the system because it would require Google services. Some use MicroG, a small open-source reimplementation that is good enough to replace the real Google Play Services for most apps (but it does communicate with Google servers similarly to the real one, so all it does from degoogling perspective is limit the amount of extra data your phone sends to Google). Then there are also ROMs that support installing the official Google Play Services and related apps. LineageOS can do that (or it can use MicroG, or just not have GPS at all), for example.
And then there is GrapheneOS which has managed to turn the Play Services into a mostly regular app that doesn’t have overreaching access to the whole system and lets you configure how much data you’re willing to leak to it.
Drivers also don’t seem to be that big of a deal nowadays, Google’s effort to simplify Android updates for OEMs has done a lot to help third party ROMs as a side effect. The biggest problem now is the various security attestation mechanisms that are available through Google Play and which Google spends a lot of time and money to convince developers to use. These are very hard / currently impossible to implement in a way that doesn’t trip security checks on the affected apps - want mobile banking? Well, that’s too bad because it will simply refuse to work if Google Play says your system has been tampered with. Workarounds exist, but they’re not reliable over time.



Generally yes. The Fn key is usually handled either by the keyboard itself or by the BIOS, and the OS just sees the resulting key presses as if the keyboard had all the buttons. Can you not find such a switch in your BIOS? Saying what vendor it is might also help someone help you.