Selfhosting single person instance?

Hello. I'm considering hosting a 1-person instance for my personal use. I'm trying to run on my own hardware, and I have used *nix for quite a long time and maintaining it wouldn't be much of a problem. However, I'm not quite sure what kind of hardware should I run it on.

How powerful should my hardware be? Say, would it be OK on a old PC with Northwood Celeron and 512mb of ram with 384GB HDD? Or maybe an android phone running postmarketOS (Alpine Linux) with MSM8916 and 2GB of ram with 32GB eMMC?

Also, my ISP does not allow opening common server hosting ports, and I'd also prefer not doing so due to security problems. Which ports do I need opened to operate a lemmy instance for my personal use (i'm only going to be connecting from home)? Can I use CloudFlare's cloudflared/Argo Tunnel to do this? (I do know CloudFlare is not great and has problems but I'm not aware of any other similar service, I'm not really able to pay for external servers but if there's an alternative service I'm open to suggestions)

Thanks for reading the post, and hopefully answering.