I have a similar project called PiKVM. I can remotely turn on my computer from a full shutdown, navigate the BIOS to select an OS, and log in, after which I typically switch to a software-based Remote Desktop which is more performant. But you can’t power on a computer and navigate a BIOS with a software solution.

Could I run larger LLMs with multiple GPUs? E.g. would 2x3090 be able to run the 48GB models? Would I need NVLink to make it work?

All I want is to host this on my server and have it download the latest offline installer of my GoG games automatically.

Xubuntu is more than fine. Tbh it doesn’t hugely matter which distro you use for this type of thing

Honestly, if it’s just a small, personal project, just use common sense and take some basic precautions (e.g. use a firewall, use NGINX instead of serving Wordpress directly, etc.).

Note that CloudFlare doesn’t protect you from everything either - it only provides some very specific services. A rudimentary level of caching images being the most common one a free account level would be able to use.