@Vivaldi OK, well, scratch that, I am going to be using it because other stuff is broken on other browsers on Linux and Orca is broken and at least I can customise Vivaldi to be as plain as possible for the screencast. Will ping you folks once I have it so you can see the accessibility issue (I’ll be comparing it to Firefox which doesn’t have the same problem – as far as I can see neither to Chrome or Chromium-based Edge.)
I do love how I was able to remove almost everything from the interface.