I find the idea of self-hosting to be really appealing, but at the same time I find it to be incredibly scary. This is not because I lack the technical expertise, but because I have gotten the impression that everyone on the Internet would immediately try to hack into it to make it join their bot net. As a result, I would have to be constantly vigilant against this, yet one of the numerous assailants would only have to succeed once. Dealing with this constant threat seems like it would be frightening enough as a full-time job, but this would only be a hobby project for me.
How do the self-hosters on Lemmy avoid becoming one with the botnet?
I don’t think you gain much from OpenBSD. It is focused on preventing vulnerabilities that are hard to exploit and unlikely used by botnets. Most dangerous are vulnerabilities caused by software misconfiguration. The OS cannot prevent your mistake. Also, in OpenBSD you will be unable to use modern containers like docker, podman etc.