@atomicpoet: Gives a rather unhelpful error message if just simply cookies are disabled in the browser:
"Don't worry, it's (probably) not your fault." → It kinda is. Or not. Mastodon fixed that already.
"Please make sure your browser is up-to-date" → It is.
"and any AdBlockers are off." → None of your business. And they don't interfere in this case.
"If the problem persists after refreshing" → It does.
"please contact your instance's administrator." → Will they tell me to enable cookies? 🙄