@switchingsocial pleroma, maybe?
I think pillowfort.io or misskey.xyz are probably the best equivalents to tumblr
What makes Tumblr for me is: a dash, much more reblogging and commenting instead of people talking to themselves on their own blog, and the long resulting threads that are blogged around forever. Also, posts that mix text, photos, videos and can be any length. And fandom communities forming. And shitposting.
mastodon.at is open to all users and federates with most instances.
🇩🇪 🇦🇹 🇨🇭 mastodon.at ist offen für alle User und ist mit vielen anderen Instanzen verbunden.