> 12-year old hardware is only marginally faster than a RPi 5

My 14yo laptop-used-as-server disagrees. Also keep in mind that CPU speeds barely improved between about 2012 and 2017, and 2025 is again a lull https://www.cpubenchmark.net/year-on-year.html

I'm also factoring in the ability to use battery bypass in phones I buy now because they are so powerful, I might want to use them as free noiseless server in the future. You can do a heck of a lot on phone hardware nowadays, paying next to nothing for power and no additional cost on your existing internet connection. A RPi 5 is that same ballpark