Chromebooks do support dual booting Linux on disk, however using legacy BIOS boot only.
I successfully installed and dual booted Fedora 40 and ChromeOS. For this I had to create a 1 MB bios boot partition in the Fedora installer, that was hinted by the installer. However I don’t like Fedora for the too many updates that make the system unstable.
So I tried Leap.
I used gparted from a rescue iso to shrink the chromeOS partition and make a new BIOS boot partition with flag grub_bios for Leap legacy booting. There is an existing EFI partition that is used by ChromeOS. This partition is 32 MB of size. I removed the legacy_boot flag, just to hint to Leap not to use this partition. Then I reboot into ChromeOS to check my changes were working.
In Yast installer I used manual partitioning and assign the BIOS boot partition. Yast complained that it does not support BIOS boot. Then in summary Yast reported that it will use the MBR of the disk. I changed it to the BIOS boot that I created.
I could boot into Leap, however not into ChromeOS. Fortunately I can recover it into a factory settings state.
Is it possible to boot in legacy:
that Leap uses a separate boot partition
or that Leap shares the MBR boot partition with ChromeOS
Please note that I am not familiar with either a Chromebook or with ChromeOS.
It should be possible to install with BIOS boot, but you seem to have been doing it wrongly.
If you boot the install iso in legacy BIOS mode, it should default to install the way you want. If you can only boot the iso in EFI boot mode, then it will attempt a UEFI install. However, you can override that.
While you are in the installer, go to the “Booting” section. If it says that the “Boot Loader” is “GRUB2 for EFI”, then change that to just “GRUB2”. That should give you the install that you want.
No, you cannot assign the “bios boot” partition in the partitioner. But as long as you set it to install booting to the MBR (usually that’s the default), then it will actually use that “bios boot” partition for booting. It will use it quietly (it won’t say it is using it). But it will use it.
I hope this is helpful. I have actually done installs this way, though not on a Chromebook.
I am a little confused by the statement “Chromebooks do support dual booting Linux on disk, however using legacy BIOS boot only”. If there is already an EFI partition used by chrome, I don’t understand why you would not use the same partition mounted at /boot/efi.
I don’t have a chromebook to test, but I would try the simple approach of sharing the existing EFI between the two oses, the same way one might approach dual boot with windoZe.
i got it working by following the tip to just used the recommended Grub summary, although the EFI system partition is not explicitly mentioned.
This time I took the Slowroll netinstall iso.
Before starting the installer, I made sure that there was some unallocated disk space. The chromeOS efi partition contains the flags: boot, efi, and legacy_boot. I did not change this.
The installer recommended me to create: root btrfs and swap.
I wanted to see the exact partitions map, so I clicked Guided using proposal.
Then I edit the efi partition of chromeOS to make sure this is mounted on /boot/efi. As this mounting was not shown in the proposal.
The installer did not complain about unsupported BIOS partition, as I did not assign any BIOS partitions.
Then in Boot summary, the ChromeOS efi partition name was NOT explicitly mentioned as being used, only the full disk name. This confused me. But I went ahead.
At the end dual booting ChromeOS and Tumbleweed is succesful.