I believe they’re available as backup but re-calibrate themselves with GPS coordinates if available. This is not a problem when GPS jamming is used but becomes an issue with spoofing - the pilots need to monitor for it.
I think they talk about it in this video by flightradar24 somewhere: https://youtu.be/4dG_Whxzdkk
re: OneNote
Although not a replacement for OneNote on Windows 10/OneNote in Microsoft 365, you can get Waydroid and run OneNote’s Android app with it.
I don’t have a stylus so I’m not able to check if everything works, but if it does, it’ll hopefully feel better than the web client, which wasn’t able to keep up with stylus strokes last time I checked. The number of pens is lacking though, even the iPadOS version is better…
It may be possible to get past that, I’ve seen people disassembling the battery to get the BMC and connecting the DC power supply to that instead.
It sounds way more risky than OP’s initial idea. I wouldn’t recommend taking apart batteries.