The multi screen sharing problem in Chromium is a known one. I've been following this patch for some time, and it seems to be close to release now: https://webrtc-review.googlesource.com/c/src/+/165724

As other commenters say, latest Fedora has Wayland and Pipewire properly configured and by enabling a flag in Chrome/Chromium (search by "pipewire") it will run smoothly and allow you to choose which screen to share.