For a few years I've been using a refurbished Dell Optiplex 9020M micro with an Intel Core i5-4570T, 16 GB of RAM, and an internal 2 TB SATA SSD… running Ubuntu Server. It works fine, but it's an old machine, and newer & more efficient low-power Mini-PCs have been flooding the market for a few years now.
I'm currently eyeing one based on the Intel N100, which, compared to the old CPUs (especially the Intel Core CPUs), is a lot better:
https://www.cpubenchmark.net/compare/5157vs2041/Intel-N100-vs-Intel-i5-4570T
For example, the Beelink Mini S12 Pro comes with 16 GB of RAM out of the box, can work with 32 GB, can house an M.2 NVMe SSD up to 2 TB and an additional SATA SSD of 2 TB, which is probably enough for a full node running Ubuntu Server for many decades worth of timechain storage, all of it on the internal M.2, with regular automated backups to the internal SATA SSD. And it's probably not a lot more expensive than an old refurbished Mini-PC.
More fun of course would be to build one yourself, e.g. with an ASRock N100DC-ITX, and a cheap Mini-ITX chassis, e.g. one by SilverStone like the Milo 10, or (if you have a home lab) a 1U rackmount chassis for better expandability, which is always possible with a DIY build.
Yes, I have been moving my RPi setups and other old micro PCs to the N100 Beelink and similar.
Faster then the PI, cheaper then the PI (once you add in the cost of case + PS + stuff) a little faster then the 4th gen i5 and a tiny bit slower then a 6th gen i5 but for applications like this it's perfect. 16GB Ram and 512GB drive for less then $175. Just swap out the drive for a 1TB ($65) and you are good to go. For $10 on amazon you can get a case for the drive that came with it and you now have a 512GB portable USB drive and it's all new. No worry about refurbs.
-Dave