Some guys in my club are running XCSoar on the Yotaphone 2. It is no longer made and the company went bankrupt but it was an interesting phone because it had a regular LCD screen on one side, and an e-ink screen on the other. It was configured to be able to mirror which meant the e-ink side could be used like any android phone (just a different screen.) The Yotaphone 3 was also a dual screen phone but it wasn’t a true mirror set up so the e-ink side was more limited. There are a couple of e-ink phone manufacturers with Hisense - a Chinese company - being the leader (I think they were involved with Yotaphone - a Russian company - for manufacturing) I have seen XCSoar running on the Yotaphone and the performance is very good because the screen quality is better than a typical e-reader, the processing power of the phones are much better, and asa result there isn’t as much of the screen refresh slowness and ghosting typical of e-ink screens. Another one introduced this year but I don’t think on sale yet is called the Onyx and it features capabilities to adjust screen refresh rates. I also posted about the new one from Hisense - with a colour e-ink screen. A little colour is all we need for XCSoar so I think it will be ideal. In fact, any of these e-ink android phones are just the ticket compared to modding Kobos and the like. As a bonus, they are not expensive compared to other cell phones.