Latitude 7400 2-in-1 cannot select files in BIOS

Disclaimer: I run a Linux setup on my 2-in-1, and I have changed the disk layout, which may be related to this issue. My EFI resides at partition /dev/nvme0n1p2

When I press F12, click "BIOS Flash Update" and click on the three dots, the system does not respond any more and the cursor does not move. The same - which is even more important - happens when I want to set custom PK, KEK, DB, and Dbx keys for secure boot.

This bug has been there in BIOS 1.9.0 and 1.10.0. I do not know about older versions.