PDF4QT, bit of a newcomer, but its a free and foss pdf editor with the capabilities of propriatery equivalents: https://jakubmelka.github.io/
Tzeentch
There's a few options
Newpipe, uses it's own extractor, also can act as a player for SoundCloud and Peertube, there's also a fork with SponsorBlock: https://newpipe.net/
Libretube, uses the Piped api, generally seen as the one with the best UI: https://github.com/libre-tube/LibreTube
Clipious, uses the Invidious api: https://github.com/lamarios/clipious
Could also watch videos in a browser from an Invidious or Piped instance I guess
And while I'm at it I'll also mention there's a client option on desktop too, Freetube: https://freetubeapp.io/
Fennec enables access to about:config, so making all of arkenfox's changes manually(by viewing its user.js and toggling it in about:config accordingly) would also be an option, none of arken's toggles are desktop only as far as I know
Your best bet is to find a car where its easiest to disable the antenna/cellular modem for, so look for a car that has a fuse for the DCM(digital communications module) you can pull, as having it be a fuse means you can readily reconnect it should you need to, try to find its schematic online, or find the repair manual for the car or use a car maintenance program,
Apparently its also possible to call the car company and ask for an opt out when serviced,
I vaguely remember some people experimenting with replacing the head unit with aftermarket ones, but no idea how well that would actually go in practice