You are not logged in.
I currently have Windows (that boots in UEFI) on /dev/sda and Linux Mint - which currently manages the GRUB - on /dev/sdb and I want to install Arch in /dev/sdc properly, without overriding the boot or breaking GRUB.
pacman os-prober already do the dirty work, making Arch part of the Mint's GRUB or I have to do something else to work properly?
Offline
You need to "os-probe" from Mint to add the kernel of Arch to the GRUB from Mint, if you want the GRUB from Mint being the "controlling" entity.
Online
You need to "os-probe" from Mint to add the kernel of Arch to the GRUB from Mint, if you want the GRUB from Mint being the "controlling" entity.
Oh, yes. After the Arch installation, right?
And if I wanted to use the Arch GRUB instead - of course, detecting and maintaining the other OSes - just do the plain install?
Offline
Pretty much, then you'd need to install GRUB and relevantly os-probe from the Arch side. Since Mint's GRUB will logistically be more dynamic and might have some more general assumptions (afaik older kernels are kept around and relevantly removed/adjusted via hooks in the relevant kernel packages) it will be less of a headache to go that way, making the Linux Mint GRUB the one that adds an entry for Arch, since an entry in Arch will be generally unchanging and updates just replace the already existing binary.
Online