Vontar X4 - no CE boot without HDMI

Received a Vontar X4 4GB -32GB a few days ago. Installed coreelec 21 (Omega) on SD card (slimbox on EMMC)
I have observed the following incident related to the Wi-Fi connection (connecting to a 5Ghz network):

  • On Android, wifi speed is good.
  • In Coreelec, without making any modification, it is quite slow (rates of 1.8 - 2 MB/s) Impossible streaming in 4K.

Connecting via SSH, I notice that the card is configured with a fixed txpower of 31dbm. By forcing txpower auto, there is an immediate increase in the rate to 12 - 14 MB/s, enough for 4k streaming.
It could be a bad default configuration set in the firmware.
I also note that establishing a regulatory domain different from the default one through the interface (coreelec settings) is not reflected in the configuration (iw reg get), if I am not doing something wrong