https://postimages.org - https://imgbox.com - https://imgpile.com are all decent alternatives to imgur (and apparently free & easy to use).
Weirdly, I’ve had some trouble with imgur myself when logging in - if I type my login and password too quickly I get a captcha pop-up show up… if I type my login info slowly it does not. Maybe some sort of anti-bot/spam security(?).
Could also be worth trying a different browser too - even if just to join up at imgur?
Good luck with it 👍