The settings page says "Warning: If you deselect Undetermined, you will not see most content.", however there is no option for this. I can't comment on other communities, is this related?
I've been able to post on some communities external to feddit.uk but not others. The Apple community on lemmy.world is one I haven't been able to use. When I hit post on my comment, it hangs. I'm also noticing some communities are totally blank or comments are missing when I view them from within the feddit.uk instance. I'm thinking there's some federation issues going on.