@marksibly Looks like Windows was installed in EFI mode and Manjaro in UEFI Legacy mode. Both modes are not compatible. Anyway, you need to change boot order in your UEFI and set Manjaro SSD first. Note that Manjaro grub, when installed with UEFI Legacy, it cannot boot a pure UEFI Installation, e.g. Windows here, so in that case you would need to choose between Windows and Manjaro in the UEFI Bootloader manually.
Install both in the same mode and it shouldn’t have problems.
The analysis from @megavolt is correct. In fact, you seem to have two disks installed as Legacy, and one fully qualified UEFI (Windows)
These are Legacy (using an MBR partition table):
Model: ATA Samsung SSD 840 (scsi)
Partition Table: msdos
Model: Samsung SSD 870 EVO 500G (scsi)
Partition Table: msdos
This is a UEFI install (using a GPT partition table):
Model: ATA Samsung SSD 850 (scsi)
Partition Table: gpt
It is (obviously) possible to have both Legacy and UEFI booting on the same machine, however, with the issues you’ve already discovered. The easiest way to overcome this, and have all booting as UEFI, requires setting only EFI booting in BIOS (check your mainboard manual), and a full reinstall of Linux, while ensuring the SSDs are repartitioned as GPT. It’s advised to completely remove the Windows SSD while you’re setting this up (replace it when finished).
That was a brief overview; I hope it’s helpful. Cheers.
Your machine’s bios has/was switched from ‘Legacy’ to ‘Uefi’ boot.
If you’re sure that you didn’t make that change yourself and it ‘just happened magically’ the reason for this is likely a depleted cmos battery, usually a little button battery on your mainboard (check manual).
If they are down and you leave your computer disconnected from mains for longer periods of time it can/will affect bios settings like hardware time and the uefi/legacy setting. Try it, you should be able to replicate the ‘magic switch to uefi’.
Obviously, how a depleted cmos battery affects a bios can not be generalised as it depends on many factors but a loss of power at this level leads to a drop to certain bios-specific defaults and ‘Uefi boot’ seems to be one of them. In my particular case, bios dropped to ‘Uefi’ and hardware time lagged excessively but my customised boot order was not affected.
And what the heck is this?
btrfs for a windows partition?
Yeah, this is a mess.
Gigabyte + Microsoft =
“Gigabyte and Microsoft, sitting in a tree… K, I, S, S, I, N, G…”
They are figuratively a married couple…
This means you should not be surprised if windows changes the boot order in your bios when you update windows. For me with a gigabyte mobo, it’s more of a rule than an exception that I have to enter bios and move the order back like I want it after every single windows update. I also quite frequently have to enter chroot and fix my grub. (my solution would be to remove/never boot windows. xD)
This also means you do NOT want to share boot partition with windows, you want manjaro to have it’s own.
As identified in posts above, it seems there is a bit of a mess, old boot vs efi boot.