I tried hosting my own instance of Primal Cache Server (since the client allows for custom cache servers), but the repository is so out of date and the README install instructions don't match the code. Based on several Github Issues posted, looks like it doesn't run on any of the latest versions of Nix and none of the run commands are available or working. I feel like if they're going to make it an option to run your own cache server, it should be maintained better to allow people to do so. Otherwise it is a bit of theater.

https://github.com/PrimalHQ/primal-server/issues/17

At this point their backend server seems to be barely maintained and/or their developers are working on it via a non-public/local repository running old versions of Nix.