I'm running Netgear N600 / WNDR3800 with OpenWRT since day one. So if you (can) plan for OS before buying, you can dodge a bullet when $VENDOR stops giving f*cks. That particular box has been released in 2011! Mikrotik is good enough (tm) probably, but it's licensed/closed-source. bcantrill once mentioned that "Infrastructure software should be open-source" and I'm adhering to this mantra for 10 years now. Dodged many bullets coming my way ... (i.e. if you want to buy something, can you plan for linux/BSD OS when vendor just doesn't care anymore?)

Would like to hear ideas about Apple's airports running custom NetBSD ... are you guys still running those as edge/internet routers with wifi or have you pushed them to the inside of the network and promoted some other box to the firewall role? I'm kinda stuck in the conundrum "it's unix with PF, it can handle itself" and "it's does not get updates anymore".

As far as I understand, no Wi-Fi 6 routers actually run Openwrt. The only way to get somewhat open software on your Wi-fi 6 or newer device is to use Merlin's fork of Asuswrt. Merlin is pretty big on not making large modifications though, so, for instance, it's very difficult to get Docker running on the device because the default Kernel doesn't ship with a lot of necessary modules. There are some nice apps that use the router directly like Diversion but I would really love a little device that managed everything from VLAN tagging to running little docker appliances and also provided a fast modern AP. Imagine an app store where the moderate power user could click and install apps on their router that all lived in little containers.