these are non foss options serveo.net localhost.run
there used to be a public instance of
https://github.com/fasmide/remotemoe but now its shutdown :( (Please come back)
there is https://ssh-j.com/ but it says "Users are encouraged to use it for SSH exposure only, to preserve end-to-end encryption. No public ports, only in-SSH connectivity"
So what are some other open source alternatives or any opinions?
Apologies if I'm misunderstanding you. It's not clear what the tunnel is supposed to do in this case.