Start9 is a diffferent approach. Most people do not want to run a server. I'm also confused about your mention of price. If you buy a $1000 server from someone else, that's more than 2 years of Federated and you don't have to play systems admin or devops person

Regarding open source. We haven't yet open sourced our control plane, and we will, but every part of the solution is open source: nextcloud, jitsi, matrix, vaultwarden, wireguard, listmonk, baserow, etc. Our control software is still in active development. The founding team at Federated Computer were behind the open-sourcing of some very significant tools in the past such as node.js, smartOS, manta. We will open source when we can best be of service to the community. Meanwhile, for customers that need a solution, it is an open-source solution because, if they want to, as you say, host it themselves to be truly "self sovereign", every one of the parts is open source and free.

Federated Computer was founded in 2021. I don't know about Fedimint.

Best.