This screenshot is a bit weird/old. Normally the menu item should be "802.11a/n/ac/ax" and not just 802.11a/n like on the screenshot. I'm fairly convinced that this option mustn't be enabled with modern releases anymore and (new) beamforming enabled by default.
On the CLI this option is also explicitly called "legacy tx beamforming".
(Cisco Controller) >config 802.11a beamforming global ?
enable Enable legacy tx beamforming
disable Disable legacy tx beamforming
Just make sure to have all options enabled in the menu "High Throughput (802.11n/ac/ax)".
