Trouble adding second drive to Grub

[Celty]

I have two hard drives:

NAME MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
nvme1n1
│    259:0    0 465.8G  0 disk 
├─nvme1n1p1
│    259:1    0   300M  0 part 
└─nvme1n1p2
     259:2    0 465.5G  0 part /run/media/uname/79edeb60-fb3d-4569-b1d5-c385f2658b09
nvme0n1
│    259:3    0 232.9G  0 disk 
├─nvme0n1p1
│    259:4    0   300M  0 part /boot
└─nvme0n1p2
     259:5    0 232.6G  0 part /home
                               /var_log
                               /.snapshots
                               /

Both of them are running Arch based distros, both were installed with the erase disk option in Calamares. Both are bootable from bios, and both have their own Grub.

What I would like, is to have the option to boot from either disk via one Grub. I have tried the steps listed in the discovery article, as well as the Archwiki.

As of now, os-prober does not seem to discover the other drives’ OS. How can I troubleshoot that?

[pebcak]

Is the other OS also using BTRFS?
I remember having a similar issue setting up a multiboot system using BTRFS.
The regular os-prober seemed not being able to discover the other OS:es.
It was pointed out to me by @manuel to use one modified by Manjaro back then and that one worked.

Packages / Community / os-prober · GitLab

[Celty]

Yes it is indeed running BTRFS, and installing the modified version of os-prober worked flawlessly. Thank you!

[pebcak]

You might need to set os-prober to be ignored for future updates and then check from time to time to see when Manjaro’s get updated and do it manually.