gab.ai is the only one I know about, its major selling point being that it's uncensored.
Additionally, when they are saying that they are not censored, can I censor it to my preferences? For example, one of the biggest problems on Twitter is lack of "negative keywords" filter. I like to follow people, but I can't control what they tweet about and I don't really care about some topics such as grammy, fashion etc. I would love to avoid these keywords, not the entire person.
Yes. There is no such thing as blocking, but you can mute users, words, phrases, tags, etc. I don't think you can set up user-specific negative keyword filters, though. If you want to filter the grammies, for example, it takes effect site-wide.
There are a lot of missing features because Gab is still young, but it has promise. I'm a little surprised they haven't opened it up to the public yet. I think they wanted to complete the mobile apps first. Apple's giving them a hard time.