I have four Huawei Mesh 3, which is a good wireless device, but it's super limited and was causing problems on my network.
So I installed OpenWrt on an Intel NUC with Intel J4125 and it's acting as a router connected on Huawei LAN port with DHCP turned off.
I'd like to have roaming feature, than I'd like to know how I could install 802.11r on my OpenWRT to take advantage from roaming, that my Huawei has (it's enable on settings).
Roaming does not require 802.11r. In fact, it is sometimes advantageous to not use this standard, as not all devices play nicely when the feature is enabled.
Traditional roaming will work simply by ensuring that all the APs have the same SSID and password. Tuning the radios such that they are running the minimum power to cover the necessary area (with minimal overlap with neighboring APs) and so that no two adjacent radios use the same channel is key to high performance standard roaming.
802.11r can be enabled on OpenWrt devices that are serving as a wireless AP, but I'm guessing your Intel NUC is a wired-only router... if that's the case, there will be no wireless configuration whatsoever, and therefore no 802.11r.