Device suggestion (AP specifically)

Hello all,
I've pfSense router with DHCP configured and 4 LAN ports.
I'm thinking of connecting one LAN port to WiFi AP (dumb) - doesn't do routing, simply provides SSID and WiFi

I am going through to figure out which AP to buy.
My criteria is : best open firmware support (WRT / Tomato)

While going through list I've few questions:

  1. Open Mesh products (now Datto): They don't have device page, are they supported very easily and don't need device page (does open in open mesh stand for easier custom firmware or is it just name)?
  2. UniFi AP Pro: seems to be supported easily (Unifi AC/mesh seems to have limitations), however I didn't find exact product at, Should I be looking for something else?

Many devices on that list don't have device page, does this mean they are not supported, or supported but installation process is trivial?

Also if this is relevant: I've gbps connection, but don't care much about speeds on WiFi (if it supports gbps that's good but not a requirement)

Actually I found
I may just buy this, it looks like exact match to UniFi AP Pro

This means nobody has created a devicepage yet, nothing more.

I'm sorry if this is too obvious.
But there are devices with support for current released version however without device page.
If I'm understanding your reply correctly it simply means: openWRT has been tested to work on device but nobody is maintaining the wiki (device page), is that so?

Unifi AP Pro procedure looks straightforward however I've following error:

UBNT-BZ.v4.0.66# fwupdate.real -m fwupdate.bin 
Invalid version 'BZ.ar934x.v6.0.0-OpenWrt-r11257-5090152ae3'

I'm following: to install openwrt


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