What type of ECC is a requirement? All DDR5 has on-die ECC but it's hard to get real ECC with error reporting. Since errors are pretty rare (about 1 / year per 100GB) and you sacrifice to get it, seems like a hard choice.
On-die ECC is not ECC memory. On-die ECC only corrects certain errors (e.g. not transport errors), and is absolutely necessary with DDR5 else such errors would be intolerably frequent.
True DDR5 ECC memory exists, and is not hard to find—just look for “server” RAM.
I wish JEDEC and the memory manufacturers had not decided to present on-die ECC as being a "feature" of DDR5 memory, when it has far more to do with the generation of the fab process than the generation of the memory interface.
There might be options in your country. But in the Netherlands there is very little choice for ECC DDR5. Only a couple model are available of 32GB 5200+ sticks; it's slow, expensive and barely in stock.
anecdotal: run the exact same system and tasks on desktops with ddr4 ecc and laptops without ecc ddr5 (they technically have amd pro apu and sodimm sockets, but i can't find the damn memory to buy)
the laptops see two unexplainable crashes per 6 mo.
