This is where I landed on this decision. I run a Synology which just does NAS on spinning rust and I don’t mess with it. Since you know rsync this will all be a painless setup apart from the upfront cost. I’d trust any 2 bay synology less than 10 years old (I think the last two digits in the model number is the year), then if your budget is tight, grab a couple 2nd hand disks from different batches (or three if you budget stretches to it,).
I also endorse u/originalucifer’s comment about a real machine. Thin clients like the HP minis or lenovos are a great step up.