pixelfed.social and metapixl.com both have active communities and open signups right now. Main reason to use metapixl.com afaik is larger file sizes are allowed (26mb vs 15mb)
edit: and you can upload 20 images to a collection on metapixl.com, instead of only 10 on pixelfed.social
also metapixl.com is based in Finland, and has some specific rules regarding content illegal in Germany etc, so they probably drop ban hammers on certain groups of abusive people harder than other servers might.
however, found the main trade-off is that pixelfed.social gives you 7GB of storage, while metapixl.com gives you only 4GB.