Fairphone with its 8-year updates, swappable battery, and decent repairability is great for those of us who doesn't like to be forced to change phones often. I'm not sure, however, what variety of distributions you mean. It supports 1 Android, and 1 de-googled Android. Which isn't bad at all, but still doesn't sound like "variety".
Wikipedia (https://en.wikipedia.org/wiki/List_of_open-source_mobile_pho...) lists /e/OS, CalyxOS, IodéOS, LineageOS, postmarketOS, Ubuntu Touch, the latter two being non-Android, the rest Android derivatives on Fairphone 5. Fairphone 6 has only /e/OS and IodéOS listed at the moment, but that will probably change after some time on the market.
There are also various reports of things like running e.g. Fedora on an FP6, https://www.notebookcheck.net/Fairphone-6-turns-into-a-Linux... or Debian on FP4/5, but those generally aren't something that is usable due to lacking support for basic things like calls.