Tzeentch

PDF4QT, bit of a newcomer, but its a free and foss pdf editor with the capabilities of propriatery equivalents: https://jakubmelka.github.io/

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