Let’s build and configure a minimal SSH bastion host (jump box) from scratch, using Ubuntu 20.04 LTS.
Source: DIY SSH Bastion Host
This is all well and good except for the bit where the author is clearly invested in using the cloud (i.e. other people’s computers) to run your own infrastructure.
Good luck fixing any of that without having to tear down a lot of your own work just to be able to be useful again. I get it, from a developer point of view setting it like this means it’s easy to plug into projects, but from a sysadmin point of view it means you’re going to shoot yourself in the foot sooner rather than later, specially if you missed a little onfiguration detail that lets your server wide open for takeover.