@linuxdev thank you for your reply!
the problem emerged from Time sensitive networking [TSN] on NX - #112 by _av
I was trying to get ntp server to autostart; I was able to do so, but it wouldn be able to read from UART only if the baudrate is set.
I was able to change it on started system from terminal with /bin/stty -F /dev/ttyTHS0 38400
but systemd, rc.local and other autostart methods wouldn’t work for setting up baudrate.
I can check it on running system with
cat /dev/ttyTHS0 unless baudrate is set there will be no readable inputs from GPS UART output