You should just set a manual rule to forward port 5023 on your Mikrotik router to port 5023 on your traccar server
yes, I did this for web service. In /IP/Firewall/NAT/ created new rule, but there is obligatory protocol to choose, list is long and contains tcp, udp and many others but nothing similar to gt06.
Since your Mikrotik router has nothing to do with traccar server protocols (it just forwards the data). Just try tcp for that port 5023.
tcp protocol is ok. Traccar receive data.
Great that it helped.
I successfully forwarding www port for traccar installed in my lan network but I've got problem with 5023 port and gt06 protocol. On the list of avalaible protocol in my mikrotik config page (RouterOS v7.2.3) there is nothing like this. I'm in path /IP/Firewall/NAT.