Quote Originally Posted by Mohammed_Ibrahim View Post
Is it that to disable UEFI?
When I go to Storage > Boot Order, I found the following:
UEFI Boot Sources
- ubuntu
- Windows Boot Manager
- USB Floppy/CD
- USB Hard Drive
- UEFI: IPv4 Realtek PCIe GBE Family Controller
- UEFI: IPv6 Realtek PCIe GBE Family Controller
Legacy Boot Sources : Disabled

If I enabled Legacy Boot Sources, does it mean that everything will be fine and it disabled UEFI?
It's hard to know exactly what it means, but in my newest computer (a Toshiba), there is a clear entry 'boot mode' where I can switch between UEFI and CSM mode.

If your computer can boot Ubuntu in UEFI mode, maybe you should stay there, and just clear the partitions. Now that oldfred has found this thread, you will get the best available support, so you will manage to get a good system, whichever boot mode you choose