TL;DR: Do. Not. Share. Boot. Partitions. Across. Linux. Installs.
------------~~~++~~~------------<
So a couple days ago I posted a screenshot of my first Gentoo install in a VM. I mentioned that I planned on putting it on my hardware in a triple boot setup (Arch - Main, BillyG-O$ - VR games, Gentoo - Pain). This is a follow-up on my adventures doing that.
Everything went well initially, I followed almost the exact same steps as the VM and things went by much faster (as it had access to all my resources). However I made 1 respectfully sized blunder, for some stupid reason, I tried to share boot partitions between my Arch and this Gentoo. DO NOT DO THAT, I can speak from ~this~ experience.
Because of sharing boot partitions, GRUB got absolutely buggered 6 ways from Sunday resulting in GRUB unable to find my Arch initramfs. Not good at all. So for about 2 days my system was unbootable (I took a break from the computer, I'd just about had it).
Thanfully though it turns out my previous Arch-only GRUB install still existed so with a quick boot override I was finally able to get back into Arch. I then proceeded to totally destroy every last trace of Gentoo from my boot drive and reinstall the kernel, thereby remaking my initramfs. My system is restored 🥹.
So, in conclusion, I feel that Gentoo is definitely good fun and worth doing, however if you're installing it on the same drive as a pre-existing OS be. Hyper. Vigilant. I'm not sure how or why my old Arch-GRUB still existed but by golly am I thankful it did.
This did not scare me off Gentoo at all because it was my error. So I'm probably going to reattempt it soon. I also jusy wanted to say thanks for the engagement and tips on my previous post, I love the Linux community and our little corner of the internet. I await the day where our pride and joy is mainstream, along with so many others I'm sure. I hope you have a great day/night :).