What is the output of xdg-settings set default-web-browser? In my case it’s set to firefox.desktop and links usually open fine.
You can set default browser using xdg-mime:
xdg-mime default firefox.desktop x-scheme-handler/https x-scheme-handler/http
More info on setting default browser: https://unix.stackexchange.com/questions/307641/cant-change-the-xdg-open-url-handler-to-firefox