It's a performance thing.

With standard 802.11 roaming, you have to reassociate and reauthenticate to the new AP. While this process is underway, you can't pass any traffic. For open networks or simple auth schemes like WPA2 single-password, this isn't very noticeable; however, for heavier-weight auth schemes like 802.1x this pause is substantial and is especially noticeable on voice/video calls. 802.11r is a scheme for caching the authentication info, letting you avoid the 802.1x round-trip to a central auth server.

For a 5-AP network, usually with shared-password WPA2, it's not necessary.

Yes, roaming by sharing SSID and passcode is a world of pain. 802.11r solves all those pains, I've been using it on OpenWRT for months without a glitch.

Yes, it's why I use 802.11r. It works with most devices, although the one which does not support it makes me laugh. Nintendo Switch will not switch from one AP to another. It holds on, tooth and nail, to whichever BSSID it used when it first connected.

My kids have to go into settings, reconnect, and move on.

afaik that is a design decision by nintendo.

i think it did support roaming in the past and they disabled it in an OS update.

I have a couple of AP AC Lites running openwrt and 802.11r, works fine except on Xiaomi phones apparently... I never tried the unifi though, flashed openwrt within 15 minutes of receiving the APs

how do you enable 802.11r on openwrt? on which model of router

Install the wpad pkg and 802.11r should show up in wireless config screens. See https://forum.openwrt.org/t/802-11r-fast-roaming-in-luci/117...

Pretty much that. It's also very simple nowadays. you just tick the box on the Wireless Security tab, and check that the mobility domain match between all the APs - it should by default, I think it's derived from the SSID.

Be aware that there might be compatibility issues. I enabled it on a pair of OpenWRT-running APs, and the handoff worked fine for my laptop, but my phone would claim to be successfully associated/authenticated with the new AP, but traffic wouldn't flow. Turning off 802.11r fixed the issue completely, and it turns out I don't really need it after all, as my devices seem to roam properly and the reauth is pretty quick.

Faster handoffs between APs.