Part of the problem searching for a lower end CPU, is that their are a crap ton of low end CPUs. It is the "server" part that tends to throw a wrench into the gears.
Yes, an older Intel CPU can work. But, their is a point when that older generation is just not power efficient enough for a practical low end server, (aka something running 24x365). Even if electricity usage is not too much of an issue, heat can be because it needs to get out of the case and the area around the case.
Sometimes I wish both AMD & Intel would design a low end server line as I outlined. Today we need enough PCIe lanes for NVMe. Even if it is not an all NVMe NAS, we still need more than 24 PCIe lanes that AMD provides on their desktop line, (24 does not include chipset PCIe lanes...)
Also to be considered a low end server CPU, having it top out at 8, 12 or 16 cores is a must. I mean the "ideal" low end server CPU could be part of a CPU line that DOES include >16 cores. But, we need choices below that for a practical low end server CPU.
As I wrote earlier, AMD's Epyc 3000 servers were nice, but today the use really old cores. AMD Ryzen Embedded 5000 series have a recent core with ECC memory support, on AM4 socket, but still has that 24 PCIe lane limit. However, the AMD Ryzen Embedded V-3000 series is just too limited, only 20 Gen4 PCIe lanes. It does include dual channel DDR5 with ECC support, and 2 x 10Gbit/ps Ethernet, (though I don't know what that means...)
Looking for Intel options has always been frustrating to me... because I'd have to check CPU against which socket, then find a board with that socket. THEN, I'd have to see if that board supported that specific CPU. It is almost like Intel purposefully designed multiple sockets for forced upgrades.
Now their are lots of people that think their ideal low end server CPU must support some feature. For example, for them, it must run their VMs, Apps, or tons of other things. So, it is all personal perspective.