GMX can't open
The website https://www.gmx.net/ can't open. After a short time comes an error message.
I can confirm this. Even with a newer useragent it doesn't work correctly. It does however work with Firefox68 so this is a Mypal68 specific problem.
Workaround: In about:config, create a new preference named general.useragent.override.gmx.net, set it as Mozilla/5.0 (Windows NT 5.1; rv:68.0) Gecko/20100101 Firefox/68.0 (or probably whatever user agent that doesn't include the word Mypal), done.
Update: Never mind, it didn't work; When the error dialog box appeared, I just deleted the part /consent-management/ from URL, press Enter, and voila. But for normal site display thereafter (without the banner that reads Reduced GMX homepage. Due to an old browser or unusual browser settings, you see a reduced GMX homepage. We recommend using a current browser.), above workaround is still required.
BTW, per-site user agent override options are removed since Firefox 71, so if Feodor2 will work on Firefox 78/91 in (near I hope :p) future, he will have to try reverting this change. (Related bug)