I want to change the ports in Syncthing to be able to port forward. I use a VPN and my VPN allows me to have access to certain port numbers that are provided by the VPN.
Is it possible to change the port numbers in syncthing to a port number that is provided by my VPN to be able to port forward with a VPN?
Yes, all ports are configurable.
Actions -> Settings -> Connections -> Sync Protocol Listen Addresses. See the documentation for the format and defaults:
(This does assume that your port numbers are more or less fixed though. If they change frequently, there’s no way to update them automatically unless your script that yourself)
default:55555 be valid for an open port? My IP address may change often but my open port number will not.
This would be treated as listen on a hostname called “default”. If you mean “listen on all/any interfaces, port 55555”, you can use
Could I do both tcp and udp on port 55555 with any IP address?
This is all explained on Syncthing Configuration — Syncthing documentation.
Syncthing only uses UDP for QUIC (which you may or may not want to use), but yes the syntax is the same.