Currently ESRT2 doesn't support booting from a GPT disk. Workaround is to create a VD less than 2TB for OS installation. Use the rest capacity to create a second VD for data storage.
After wasting hours of trying, I have indeed given up on that. I'm using SRT now (basic intel raid controller) and split up the partitions in 2 x 1800TB raid 10.
Is there any difference in performance between the 2? SRT vs ESRT2
If so, I might reinstall the thing again, but with the VD less than 2TB like you said.
Both RST and ESRT2 are software RAID, not much performance difference is expected. Actually main difference is that RST supports RAID 5, while ESRT2 has better Linux support. For more details, see Comparison of Intel(R) ESRT2 and RST (Matrix) RAID.