> Their product lines are confusing mess requiring looking up each specific part to get a list of features it does or does not support. There's little rhyme or reason to it.

I got bitten by that back in the Core 2 era. When I built my very last Intel system, around an Intel DG43NB board, I picked up a Q8200, thinking it would be a great bang-for-the-buck chip. Little did I realize from the store display that the Q8200 was the only Core 2 Quad that lacked virtualization support.

The DG43NB died prematurely, due to capacitor plague. I didn't shed any tears for it.

Since Haswell, ECC support has been on (Core-based desktop) Celerons, Pentiums, i3s, and Xeons. It's quite straightforward, when they pulled 2C Xeons off the market they added it to the consumer processors instead, but they still want to retain Xeon sales for the higher-end products so they lock it off on the i5s/i7s/i9s.

Of course you need to know what you're looking at, the suffix of the number matters a lot (eg 7100 vs 7100U), but that is nothing Intel-specific. A Ryzen 2700 and a Ryzen 2700U are very different processors as well.

The issue isn't that somehow the 7100U vs 7100 is some fundamental design decision that didn't include ECC support, its that Intel had a chip where ECC was supported, then disabled it.

Its not because they are "very different processors".

The 7100U is a BGA laptop processor. You're not in danger of accidentally buying a 7100U to put into your NAS.

If you look at the products that are actually compatible with your system, it's not confusing at all. Pentium/Celeron/i3/Xeon = has ECC, i5/i7 = no ECC.