I've got this one from AsiaRF: https://www.asiarf.com/shop/wifi-wlan/wifi_mini_pcie/wifi6-4... . OpenWRT has drivers for it in the repository, so it's pretty simple to set up.

I'm happy with it, but I did have to get a heatsink for it, since otherwise it overheats easily. Since I got it they released a couple of dual-band dual-concurrent cards like this one: https://www.asiarf.com/shop/wifi-wlan/wifi_mini_pcie/wifi6e-... , which is pretty neat, since you don't need to get a separate card for 2.4GHz devices.