How old is “older?”
I run the latest Debian on a 10 year old Macbook Pro. Linux has given this laptop a second life as a lab machine - it’s still plenty fast enough and it has a really nice screen (Retina) which Debian gets right out of the box with no tweaking. The only thing I needed to do when installing Debian is manually get the drivers for the WiFi hardware during the install (although Debian has the non-free firmware by default these days, they aren’t permitted to distribute all firmware and the WiFi hardware in this machine unfortunately happened to be one of those).
As a workaround, you could use OBS and use OBS’s virtual camera so Discord is streaming what it thinks is a camera, and set up whatever you want to share on your desktop through OBS.