…sounds similar to my mess a couple days ago, after installing Ubuntu, and Mint,…
i ran into a similar, but much worse issue, when I was playing around with installing mutiple manjaro’s, via m-a CLI-installer:
Needless to say, the multi-manjaro’s were fine, but i also installed a few Ubuntu/LinuxMint uefi/gpt installs along the way, along with UbuntuStufio 17.04, and then it all got fscked up.
btw: everything was setup/installed in grub2/uefi/gpt mode.
And yes,i even tried all the braindead Win10 solutions of useless things like this:
Or even this bait-n-switch mess:
none of which worked.
Instead, I ended up with a:
The ONLY thing that [allowed me to boot into Win 10], was that “manjaro-grub” efi bootloader that I wasn’t even sure about?. -same as you.
will show you that manjaro, and manjaro-grub, should point to same deivecs?
Everything else failed with “Missing Operating System …” weird enuf ?
And even then, I could not get into a proper grub2 bootmenu unless I typed “exit” at the useless “grub>” prompt.
…it was that bad.
Even when I finally decided to wipe everything off of the disks, the stupid nvram/uefi, in my Gigabyte MB still kept showing me dozens of the same dead boot entries. !?
However, “efibootmgr”, from a bootable, did solve that problem of clearing boot entries,
BUT, I could NOT boot back into Win10, no matter how many “update-grub” I used. My damage was done, but atleast you still have a "“Boot0000* Windows Boot Manager”.
I had to reinstall Win 10, and start again.
Obviously this all may not help you, but I’m jus letting you know what I failed at.
Your situation may be different?, maybe not.
Even Microsoft’s PnP -[plug-n-pray] was never as bad as this non-standardized uefi/gpt fiasco is.
With Bios/MBR I have never had any problems such as these, but hey, if they wanna blame the User, then I’m ALL ears.
Either way, there’s some interesting troubleshooting ahead.
Gotta start somewhere again.