I'm not getting the option to boot into manjaro from the Ubuntu grub

Hello everyone,
I have a drive (240GB) and I have partitioned it as - 60GB, 60GB, 120GB. Before the manjaro install it was 60GB and 180 GB.
I have installed Ubuntu on the first partition 3-4 months ago and I’ve been using it since.
But I wanted to install manjaro on this drive too so I created another partion of 60GB and went ahead with the install using live environment, everything went without a hitch.
After the restart when booted into the said drive I was greeted with the Ubuntu grub but I can’t seem to get the option to boot into the manjaro.

It is an external HDD connected via the USB port. I use it that way because of some portability constraints.

The drive was connected to a Dell laptop (i5-5200u, 920M, 8GB ram) when I installed the manjaro. It has windows 10 installed on the default internal drive.

I’ve tried to be as comprehensive as possible with the details of the circumstances. Please let me know if I did anything wrong or is there a way to get the desired results i.e. getting the option to boot into manjaro from Ubuntu grub.

Because ubuntu grub cant boot manjaro.
Manjaro’s grub can boot most anything.
When multi-booting with manjaro you should use manjaro’s grub.

1 Like

How would I go about doing that? And would the manjaro’s grub be able to capture Ubuntu? I’m fairly new to the whole Linux space so I’m sorry if these are dumb questions.

https://wiki.manjaro.org/index.php/GRUB/Restore_the_GRUB_Bootloader

this might help:

Yes.

Once upon a time this was as simple as running sudo update-grub from within manjaro.

But you may need to go a bit deeper and do something like this:
https://wiki.manjaro.org/index.php/GRUB/Restore_the_GRUB_Bootloader#Reinstall_GRUB

@ishaanbhimwal yes @gohlip wrote some extremely in-depth tutorials that could apply here as well … though I couldnt quickly find a pertinent one.

the most reason is :
Ubuntu stays with version 2.04 Grub that do not support multi-files on boot ,
since start grub Manjaro , we boot with microcode & kernel , not just kernel

also Ubuntu require a shim/key from micro$oft that has been change 2 times , and give now lot of headhache with all UEFI version with SecureBoot , because they have to refuse older keys/shim( included micro$oft versions ) .
this happed 2 times boothole 2020 and 2021 grub

Ubuntu do not use last version release , because it include multi-files boot patch
and there are theses bugs
https://savannah.gnu.org/bugs/?61622
https://savannah.gnu.org/bugs/?60458
https://savannah.gnu.org/bugs/?61233

see this and date about version 2.04 ( big changes on march 2021 )
https://git.savannah.gnu.org/cgit/grub.git/log/?h=grub-2.06

also for any others Distribution DE , they have more than 100 - 200 patches that they cant now revalidate