You can also automate this with autossh which is designed for exactly this kind of persistent tunnel. Although a simple “while” loop might seem like the intuitive way to keep it running, autossh is very reliable and takes care of all the corner cases for you.
It is mostly a myth (and scare tactic invented by copyright trolls and encouraged by overzealous virus scanners) that pirated games are always riddled with viruses. They certainly can be, if you download them from untrustworthy sources, but if you’re familiar with the actual piracy scene, you have to understand that trust is and always will be a huge part of it, ways to build trust are built into the community, that’s why trust and reputation are valued higher than even the software itself. Those names embedded into the torrent names, the people and the release groups they come from, the sources where they’re distributed, have meaning to the community, and this is why. Nobody’s going to blow 20 years of reputation to try to sneak a virus into their keygen. All the virus scans that say “Virus detected! ALARM! ALARM!” on every keygen you download? If you look at the actual detection information about what it actually detected, and you dig deep enough through their obfuscated scary-severity-risks-wall-of-text, you’ll find that in almost all cases, it’s actually just a generic, non-specific detection of “tools associated with piracy or hacking” or something along those lines. They all have their own ways of spinning it, but in every case it’s literally detecting the fact that it’s a keygen, and saying “that’s scary! you won’t want pirated illegal software on your computer right?! Don’t worry, I, your noble antivirus program will helpfully delete it for you!”
It’s not as scary as you think, they just want you to think it is, because it helps drive people back to paying for their software. It’s classic FUD tactics and they’re all part of it. Antivirus companies are part of the same racket, they want you paying for their software too.
Matrix and its implementations like Synapse have a very intimidating architecture (I’d go as far as to call most of the implementations somewhat overengineered) and the documentation ranges from inconsistent to horrific. I ran into this particular situation myself, Fortunately this particular step you’re overthinking it. You can use any random string you want. It doesn’t even have to be random, just as long as what you put in the config file matches. It’s basically just a temporary admin password.
Matrix was by far the worst thing I’ve ever tried to self-host. It’s a hot mess. Good luck, I think you’re close to the finish line.