This isn’t a recommendation from me but here is someone reporting a well-behaved one: Terrible WiFi performance with Librem13, Librem15 - #99 by Dreamr
Probably depends on which other distro. Definitely Ubuntu?
You can definitely add other repositories. In some cases that might create a mess. In other cases it should be fine.
See also Installing evolution-ews (your own enquiry). Maybe follow up there.