I did what rigking said and it saved my miner.

This said I would add 2 things:
- the SD card must be FAT32. It happens that my card was 64Gig, and therefore exFAT and not FAT. The miner was just ignoring it. I had to partition it, so I can format it using FAT32 and then follow rigking instructions to succeed
- After the miner booted on the SD card, I removed it and restarted the miner, which still had the 2019 OS on it. Therefore I did put back the sd card, booted, and then was able to flash a new OS (Hiveon) on my L3.

Note: I am still denied SSH, which may be normal (frankly I have no idea) with Hiveon asic software

Huge thanks to rigking for the links and the tip to overwrite with an old version...