For the former, I would imagine `rsync -Pav $whatever_old_ff_profile/ $HOME/snap/firefox/whatever/` would do that, since AFAIK snaps store user-specific persistent state outside of privileged directories

The alternative, and likely why no one has applied a great deal of pressure to that workflow, is to use the Firefox Sync account they've been pushing so hard

Netflix for me works fine. You just need to tick the 'Play DRM content' setting.

My personal reason to use the snap is because it limits access to the home directory. So I can disconnect my home directory, camera and microphone and have a second layer of confidence that my browser won't leak any personal data.

That and it avoids Firefox leaking config files in my home directory.

If I want to upload a file, I simply move the file into a Downloads folder in it's SNAP home directory. This way, Im in control of what the browser can access.

By default, a snap package cannot touch your dot directories in your $HOME. That is good for your security.

You would need to copy once (or `rsync`) from `~/.mozilla/firefox/` to `~/snap/firefox/current/.mozilla/firefox/`.