unfortunately not anymore,
in the early days of firefox sync back when it was called wave it was easy to selfhost. Just throw some[1] php files to a host and it worked.
Then mozilla changed it to use multiple services (auth, ...)
it got difficult and the documentation wasn't easy to access.
At that time i stoped selfhosting & using it :(
[1]: https://github.com/balu-/FSyncMS