A notable mention is https://ubports.com/en/ which is different from postmarketos in a sense that ubports uses old kernels with heavy patches. That means: good support for things, but difficult future.
PostmarketOS uses the newest kernels and tries to integrate their patches into mainline kernel, so that the reliability is maintained with all kernel developers.
Cool, does it run on a Galaxy Xcover6 Pro with a Verizon plan? I bet it doesn’t, nothing does besides the big-2 OS’s it seems.