I don't think Mozilla has a recent write-up (blog post) about the Sync Server. The most recent one I found is an announcement from 2020, which explains some of Mozilla's motivations:

https://blog.mozilla.org/services/2020/09/15/the-future-of-s...

But, as you mentioned, the current documentation is here:

https://mozilla-services.readthedocs.io/en/latest/howtos/run...

You might also find the unofficial Arch User Repository package, comments, and PKGBUILD file helpful:

https://aur.archlinux.org/packages/firefox-syncstorage-git

I hope it works out for you!