What is your definition of stability? I have used Arch for about ten years without any major breakage, but sometimes you do have to do some manual tinkering if a package stops working. So it’s stable enough for me, but maybe not for others. Since it is a rolling release, packages are generally being updated quite rapidly.
I think that any modern rolling release distro would fit the bill though.
Take a look at Group-Office. It has a community edition that is self-hosted and a paid professional edition. You can either self-host or host in their cloud.
https://www.group-office.com/
Full disclosure: I am one of the developers.