I selfhost on a cheap VPS I found on LowEndBox. The security setup (not SimpleLogin) was more involved than SimpleLogin. Pretty easy to get working and I’ve had not a single issue in 1.5 years of selfhosting it. I pay $11/yr for the VPS compared to $30/yr for SimpleLogin.

With regard to your specific questions - I’ve only selfhosted for myself with one domain. You can add multiple users and domains though.

Liner lock knives have been around for decades, I think that suggests there isn’t a problem when used correctly. The benefit is that you get a very secure folding knife when the knife is extended, and you can fold it with one hand.

No such mechanism. Sharp things are inherently dangerous - go slow, pay attention, and you’ll be fine.