For my Bitcoin node, I don't use any pre-packed node software. I built my own. I have used Umbrel and Start9. I would recommend both. Umbrel is more user friendly. Start9 is more robust, but less user friendly. If you want to learn about Linux and build your own node you can follow this guide. https://v2.minibolt.info/ I ran Umbrel for nearly 3 years, StartOS for a week, and then built my own because I'm a power user and wanted to do more.

For a Nostr relay, I've been using the Nostream relay since last December. It's easy to run, if you're familiar with Linux and docker. Here's an older guide, it's for a paid relay, but you can just not turn on that option. https://andreneves.xyz/p/how-to-setup-a-paid-nostr-relay

Use it as a learning platform then, you have the hardware already, and you have done half of the work :-) Stuff like Kubernetes and containers, in general, is well worth learning, you can land a job if you are persistent and like it. I would encourage it. Find out what you want to learn: app development, infrastructure management, etc., and do a deep dive...

Not really a guide but for starters you should check whether your hardware will actually run the new OS or not. I suggest start with ISO image burned to USB drive and boot your laptop from there, it will ask for options so pick live iso, this way it will not touch your HD unless you tell it to install full version. You basically run full OS from USB to test so it will not be fast. You can get light Ubuntu Budgie desktop to test - https://cdimage.ubuntu.com/ubuntu-budgie/releases/23.10.1/release/ubuntu-budgie-23.10.1-desktop-amd64.iso It gives you kinda macos feel without apple crap...lol Then read/learn about it, learn some more (actually really read the docs, they pretty decent) and see if that's something you like...