Tumblr works well provided you are in to that kind of posting/fandom. They haven't enshittified their web ui, so you can access the website without the use of their app. You can easily sign up with an email alias and use a VPN for location/IP.

Firefox and its forks like Fennec and Iceraven let you install a website as an "app" and the feel is essentially the same (on android, not sure about ios). Slap on Ublock Origin, Privacy Badger, and Noscript and isolate in a sandbox or work profile and you have a pretty good setup, despite using a mainstream service.

There's also the fediverse ofc. Pixelfed offers an experience like Instagram, and Loops is similar to TikTok/Shorts but with smaller communities and creators.