Hi, and first of all, thank you fohdeesha and all for this method
I managed to eventually flash two H710 D1 mini's to IT mode, but not without problems during the process.
First of all I must remind everyone to read and fully understand the instructions before attempting this. I read the instructions multiple times and still missed some important steps, for example to note down the SAS address for the second card I flashed. But luckily in my case I just used the same address from the previous card, which I also almost forgot to note down. The cards wont ever be in the same server so I don't think having two cards with same SAS address in different servers to be any problem.
With both of the cards I really struggled to get them working. I had removed the battery, but still both the cards would fail the D1CROSS script part where the flash gets erased. Some times the erase would end in error in 10% of process, some times 30%,40% and so on. Some times the first pass would end in error but the second would go to 100%. The most important part however, the SBR write process always ended in Success.
To make sure the flash was erased I just plugged the power off from the server (to get rid of the PCIE fault halt problem) and ran the D1CROSS as many times as needed to get at least once 100% erased flash and success with SBR write.
After this it was time to boot to Linux, and with this I had to define iomem=relaxed or I would get the mmap bar1 problem,
mmap bar1: Invalid argument · Issue #6 · marcan/lsirec
I first followed the instructions and ran the D1-H710 script, but this would always end in errors, usually when trying to erase the flash (menu option 3), or erasing the ?persistent manufacturer info? (menu option 8). Some times the new firmware would get flashed, but somehow partially or there still were some parts not erased correctly as the info command would struggle the get info from the card.
To solve all this, I just followed the steps in "Technical explanation"
reading SBR from 2208 shows the data to be offset by a few bytes · Issue #1 · marcan/lsirec and ran the commands one by one. After this and reboot the card info was displayed without problems and I could finally write the SAS address. I'm not sure this is the best way, but at least for me both the cards flashed with this method are working OK.
So, in overall, make sure you know which card you have, after this there shouldn't be any major issues to get the card either working with the new IT mode firmware, or to get the card back to original stock RAID firmware. At least for me even if I had major problems with flashing to IT mode, I still got the first card successfully back to the original firmware, just to confirm that the card was working and that my problems were not due the card being somehow bricked.