Click reply (not typing a response, just needed to get it in "action" mode)
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Only after these steps I see a forum with the top bar and my login profile pic. Cant just go to forum.arduino.cc and choose login, as there is no login option on screen.
Using Firefox latest on OSX.
So IMO this is tres ridicule, and needs some polishing and testing on your behalf.
Weird. I use firefox on a Mac (running somewhat old MacOS), with a bookmark to https://forum.arduino.cc, and I get a pretty prominent "login" box in the upper right...