"Operation System not found" message on Dell Inspiron N7110 laptop

[Deleted member 108694]

or try

sudo grub-install /dev/sda/

then run

sudo update-grub

I usually turn off UEFI and TPM2 since Linux does not need these to run - I change that in the BIOS by setting it to Legacy and end up with this simple partitioning

 

[enluk]

Thanks to everyone involved for their help. We succeeded, although it was not easy.

What helped in my case:
1. update of the modded BIOS, with access to UEFI settings
2. preparing the partition beforehand, because by default the installer did it differently every time.
3. proper installation from USB prepared in RUFUS. Usb prepared in etcher unfortunately did not work.