> If you really, really need to poke holes into your firewall can easily that with ssh to a cheap vm hosted at your trustworthy hoster. If ssh ain't enough, nc and socat are your friends.

Wouldn't that still be the same, considering ngrok is just doing the tunneling. In this case, ngrok is your trusty hoster. You can park your trust into your own VM in Digital Ocean, or you can park it at ngrok.