While I’m absolutely for reusing old hardware and am doing it myself, keep in mind that the security landscape has changed. Old hardware might have security vulnerabilities which could be exploited by malware. Running an up to date OS is not enough to keep you secured.
To be fair, those tech upgrades aren’t exactly trivial to do, and most programmers aren’t skilled enough to do it.
These kinds of projects need very careful management to avoid running overtime and over budget.
I actually tried it before for my TV PC that I wanted to also use as a miniserver, with gpu pass through and everything. It was painful to get it working properly, was like 30-40% slower. I also had constant problems with USB peripherals not connecting properly, or going in a sleep state and not waking. Many games didn’t work properly.
Then I decided to just buy a cheap second second hand PC and never looked back.
Did it work? There’s a huge chance of data corruption if you are copying the disk of a running system.
Or maybe an automated system flagged it and an underpaid and overworked employee in a third world country reviewed it.
I don’t think this was malicious, these app reviews are being done by an overworked and underpaid employee in some third world country. Mistakes are made all the time.
Make a plan. Think about how much storage you need, whether you need redundancy and backups, and what server applications you need to run.
Here you also need to consider how much time you want to spend on maintenance. Premade solutions like Synology are set and forget. Using NAS operating systems mean having to do regular updates. Using just Linux is also an option if you want full control and are confortabile with the command line, but it’s more work.
Then step 2 is getting the hardware.
My recommended route, if you want to spend the least amount of money, is to get a 2nd hand PC, preferably not pre-built (dells and hps have proprietary parts like power supplies). A 4 core cpu from the last 10 years should be fine, and 16gb of RAM is more than enough for most applications. SFFs or MiniPCs might be ok for nvme SSDs only, but if you want hard drives, get one that has enough HDD bays. Depending on what you find, you might need to replace a few things, like the power supply or case.
Servers are good and reliable and have nice features, like network management, redundant NICs, redundant power supplies, but are usually pretty noisy.
Easier to install puppet governments than try to integrate more angry people into the population.