As of this writing there appears to be only two supported 6E devices. Adding support for more 6E devices is dependent on volunteers buying such devices and poking around bootloaders and device tree files, so I would not expect the situation to change significantly before the end of the year.
If you absolutely insist on 6E, there is the Acer Predator W6. Support for that device has been merged into OpenWrt and stable builds are available on the firmware selector. I have no idea how well OpenWrt works on it.
If you don't mind the gamer aesthetic and the 300 USD price tag, that is one of the two 6E options as of this writing. The other one appears to be a ZyXEL device with ISP branding, so availability is far less.
Honestly though, I would stick to WiFi 6 for now. There's lots more supported WiFi 6 devices, almost all of which are much less expensive. Also, WiFi 7 is already around the corner. If I had $300+ and lots of time to spare on WiFi I'd rather spend it on a WiFi 7 device and try getting OpenWrt running on it instead. 