What would you do with this old PC if you had €0 to invest in it?

I have an older desktop sitting around with:

• AMD FX-6100, 6 cores at 3.3 GHz
• NVIDIA GeForce GT 730
• 24 GB RAM
• ASRock 970 Extreme R2.0 motherboard
• One SSD and one HDD

It still works, but I currently have no money to upgrade it or turn it into an ambitious homelab project.

I am trying to decide what would be the most useful and least wasteful thing to do with it.

A few possibilities I have considered:

• Install a lightweight Linux distribution and use it for experiments
• Turn it into a local server, NAS, self-hosting box, or automation playground
• Use it to learn more about local AI, although I assume the GT 730 is far too limited for most modern models
• Keep it until I have money for a few upgrades
• Sell it cheaply and put the money towards a newer, more energy-efficient machine

My main concern with using it as a server is electricity consumption. Keeping an older FX-based desktop running all day might cost more, both financially and environmentally, than the practical value it provides.

What would you do in my situation?

Are there any genuinely useful €0 experiments this hardware is still suitable for? Is it worth keeping, or would selling it or reusing the parts elsewhere be the more sensible choice?