TRX40 doesn't really support ECC RAM.

Not in a way that matters. Those boards are consumer chipsets, not workstation platforms.

Threadripper CPUs themselves can handle ECC, but the TRX40 chipset and most of its motherboards treat ECC RAM as regular unbuffered memory. You can physically install it, and it will boot, but the error-correction features just won’t activate. You’re paying extra for chips you won’t use.

If you actually need ECC for stability or data integrity, you want Threadripper Pro on WRX80 or a Ryzen-based system (where ECC works with the right board). TRX40 is for fast memory, not safe memory.

Save the ECC money and buy faster non-ECC sticks instead.