For a small pocket and low power consumption but incredible performance I would recommend the Odroid M1. Add a cheap nvme drive for the os (I prefer debian) and a 2,5" hdd. On top of debian you can install OMV for a webui based linux home server control. DietPi is nice for beginners too. And like other ppl already said, you can use docker/podman for running your software.

Oh and don’t forget the 3-2-1 backup rule. 3 Backups, 2 different media types (ssd, hdd, usb stick, cloud, …) and 1 offsite backup (cloud or hdd at your friend’s house).