I found a bug please users to confirm.
Devices with WiFi Mikrotik on IPQ -4018/19.
If you select Data Rates configured uncheck all the boxes with A/G as well as all modulations HT MCS leaving only VHT MCS, the devices stop measuring the signal strength. If such settings are made only on the access point, the signal tab shows 5.5 MBit modulation, which should not be in the 5 GHz range, it is 802.11B modulation. If Data Rates configured and on the client, the access point can not measure the signal strength at all. It shows a signal to noise ratio equal to the noise level. First encountered on LHG XL 5 ac, checked on hAP ac², such settings lead to a sharp deterioration of the connection, the connection speed drops dramatically. Checked on ROS 6.49.8 and ROS.7.13 driver wireless
If you turn on any HT MCS then the signal strength readings appear.