leifb
Yeah so its a UEFI install which means its not grub, it is using systemd boot.
I guess the merging you've done also explains the weird sda2,5,6 (missing numbers). My theory now falls to Solus trying to install the kernel to a dev ID that no longer exists. sda1.
At which point IF I am correct. I would backup and reinstall because I'm not sure how to fix that. Maybe someone else can help but yeah at this point, looks like a nightmare to me 😛
Sorry.