> https://askubuntu.com/questions/889164/use-phone-as-microphone-in-linux
This looks interesting, indeed (tho Plumble is not maintained any more
AFAICT, you might be able to use Mumla instead, also available from F-Droid).
> https://www.bytesin.com/how-to-use-your-phone-as-a-webcam-on-windows-linux-and-macos/
AFAICT these are all proprietary software, so I wouldn't recommend them.
Stefan