This site is interesting. It lists 200 phones that can run Linux and how well they can run it (alpha, beta, etc):
http://many.tuxphones.com/
My Galaxy S9 isn't listed there, but it runs Ubuntu 16.04 through Linux on DeX. So does the S8, S8+, S9+ and S10. Unfortunately, Linux on DeX is being discontinued.
My LG G7 and ZTE AXON 7 mini are not listed. The LG G7 was introduced in 2018.
Does the Axon 7 mini run a version of Linux? How?
It's just 200 phones. And it's early release, just came out on November 10th. So nobody said it was complete. :)
You can read more about it here (https://tuxphones.com/announcing-many-tuxphones-com/). It scrapes websites to find info about supported phones so it probably just hasn't scraped the right ones that cover the galaxy s9 for example. So don't despair if your phone isn't on the list. My phone isn't either but I happen to know it's not supported from other sources, at least not since about 6 months ago when I last checked the various websites.
I wasn't despairing; it just showed me that the list wasn't complete. While I will demo Ubuntu on DeX when I next present, I don't take any joy out of my phone running Linux on DeX, since it is no longer being supported. It would be great if someone would pick up the Linux on DeX project and run with it.