I changed it from the TCP/UDP that I had it set to to just UDP, but that didn't work unfortunately. I've added a screenshot of my port forwarding settings.
This issue is mostly resolved. The Switch does seem to save the player skin when logging in to the Microsoft account once, but content still does become unauthorized if the account can't be logged in to. It is an improvement however.
Thanks for reaching out to me. Please close this ticket.
I'd like to report that this issue has been resolved with server version <bedrock-server-1.19.31.01> and that this ticket can be marked as resolved. I have tested it today with the latest updates and was able to connect successfully with my Switch.
Cheers!
Ryan