Did you just upgrade Manjaro and now your Artix will not boot, or vice-versa?
This is a peculiarity of grub in relation to Artix, and Manjaro, and I suspect all Arch based distros. When Artix or Manjaro make grub entries for all other installations found on the system (other than those from the same family) they use the universal entry template for generic linux distros. The entry they make for themselves is different and if it is not done this way they will throw the installation into “kernel panic” and this would be the last thing written on the screen before you pull the plug as no input will be recognized. It is all on the format of the commandline that grub uses to start up the kernel. [note: in the early days of Manjaro-OpenRC when I still had Manjaro-systemd still installed, they both made correct entries for each other.]
Now listen to this! Artix (to both Manjaro-OpenRC or Arch-OpenRC) is a substitute for those two discontinued projects. Let’s say you are hard headed enough to keep a copy of the obsolete discontinued distribution and have installed the new one beside it, among other installations. When Manjaro finds Artix it treats it as any other linux distribution, and formulates the grub entry just if it was Debian or Void or Devuan. For itself it makes a custom entry so it can boot again. This is semi-excusable for Manjaro not knowing Artix very well, being the new kid in the block. So now, your Artix will not boot.
When Artix builds its grub menu for multiboot, it does the same exact thing for Manjaro. So Manjaro will not boot from the Artix grub menu, and Artix will not boot from the Manjaro menu. Guess what? The format they both use for themselves is EXACTLY THE SAME!!! Everything else works with either one of them, but neither will work with the other’s grub entries. It used to be simple to have one of those weirdo grub-booters handle grub for the whole system as what they configure works for all other non-Arch based systems. But now, if one has two of those weirdo grubers on, either one will mess the boot sequence for the other.
So what is there to do? Decide which one of those idiosyncratic distros you want to handle all grub, then “update-grub” on the other when necessary, maybe due to kernel changes/updates, and then edit “/boot/grub/grub.cfg” search for the first menuentry, copy till the } bracket ends below the last submenu entry of that installation, and paste it in the main grub handling other weirdo. It is best to have grub on the most active installation of the two or more, and copy the entry from the least frequently updated system. Then make a backup for the menuentry of each one of those weirdos so you can cut and paste without partition hopping (ie make a menuentry stub and call manjaro.cfg stored on both artix and manjaro, and the same for the other). If grub, or grub-pc, get updated, the “pacman” will go and reinstall itself on the disk as “it” being the manager to start all other installations. So you never know when you will need that patch.
To install grub by any linux ditribution that has grub, use sudo grub-instal /dev/sda (or sdb or whatever your system’s disk name is). If you want to transfer control to another go to it and it will boot based on that system’s /boot/grub/grub.cfg. If you know of a better way around this “bug” that none of the developers will accept as a bug, please let us ALL know. The developer will tell you that it is not a problem or an issue if you let their distribution handle grub. But Devuan can say the same thing or Ubuntu or practically any of the 1500 distros out there, and then your Artix, or Manjaro, or possibly Arch, will not boot. In all my research I have found NO EVIDENCE of the advantages of the alternative routine for booting those distributions. Now, if only Grub team would listen and create a script to identify the peculiar weirdo distributions and use their alternative template the problem will be solved.