> when you register on a small instance, people’s profiles are empty, there are no posts, hashtags do not work.

Not a big problem for me, I just go to big instances like mastodon.social and find content or people I'd like interact with. Being registered on some instance doesn't mean you shouldn't visit other instances.

> THUNDERBIRD: the SUCCESS STORY of LINUX!

And still no native unread mail tray indicator under linux.