Hi There,
I finally built it, following your advices I’ve finally opted for ECC capable system.
Motherboard Supermicro M11SDV-8CT-LN4F (310€)
- AMD EPYC 3201 8-cores (11 Watts idle)
- PCI bus 3.0
- 4x SATA ports
- 1x PCI x16 (support 8x8 or 4x4x4)
- 4x ECC RDIMM slots
Parts :
- 4x16GB@2666Mhz ECC RDIMM Samsung M393A2G40EB2-CTD (70€)
- 2x240GB Crucial BX500 SATA SSD (boot disk) (50€)
- 1x M2 to 5x SATA ports controller JMB585 (46€)
- Case Jonsbo N2 (187€)
- PCIe network adapter 10Gb SFP 82599 (X520-DA1) (45€)
Total without data disk : 708€
Installed true nas scale, all devices are fully recognized. 
Note : I spent 2H trying to figure out why that IPMI Gb port was not coming up… => By default there is a jumper setting that disable that port