thanks for the reply. Fireox is my standard browser. I have tried chromium-ungoogled & Falkon. All say that my browser is not supported and that I should use either chrome, opera or edge. I have just seen that Falkon uses AppleWebkit :-/. I'll have to investigate more browsing possibilities.

I have just tried Brave - same error. Can you suggest a browser I could try?

As long as you don't use Gnome web, which uses Apple's WebKit, then you would be safe. Which browser are you using?