Asking for some help on Ubuntu. I have three different browsers installed but I cannot select a different default browser in the System/Apps/Default Apps settings. The options box just shows Firefox with no drop down arrow or different choices at all. 
The other two I have installed are Vivaldi and Zen, but it's like the OS doesn't know they are there.
Am on 25.10, this was the same situation before updating yesterday though.
UPDATE: Sorted out now, Vivaldi was installed from flatpak, Ubuntu couldn't see it, installed Snap version of Vivaldi instead, there it is as a choice in default settings.
I have a feeling I avoided doing the Snap install originally due to seeing some negative chatter about it, but I really can't remember exactly now. Thanks for your help provided in the replies.