disroot and autistici have been providing decentralised communication services (like email) free of cost for many years. They are both run by activists and survive on donations, and they don’t spy on you or get any money from your data. Also they run freedom-respecting software, so all their code is publicly auditable.

There’s paperd.ink introduced some years back at IndiaFOSS

https://docs.paperd.ink/docs/software/examples/