So I've seen the TP-Link and GL.inet travel routers, and it looks like some of the GLs are/were built to run wrt firmwares. Stock TP firmwares have been pretty full features in my experience. I really want USB-C power. The GL wireguard support looks useful too, but it looks like their newer stuff is proprietary? Another want, not need, is 5 GHz band.
Does anyone have a favorite model or another board that can be flashed?
As others has pointed out, I'm using the GL.inet 750s (slate), I'm in a hotel right now using it! I got mine several years ago and I'm not sure how easy they can be found now. Like you pointed out, I wanted to run stock openWRT on it, it wasn't available when I first bought it, but now it is a supported device. It's nice, I keep two backups, one for wired ethernet (when the hotel has it) and the other is for wifi where I connect the 2.4 radio in client mode to the hotel internet and the 5ghz radio in master mode as an AP and bridge the ethernet ports. It works well, but it does have a micro USB for power.