Okay, if you find it, let us know.
Normally, any OS detected by grub will boot, even if that OS does not have grub.
Can’t say that for any other bootloader.
If you need help with the path, you’ll have to show the contents of /boot down to the solus.efi file. Look at the $esp partition only, no need to look elsewhere. Oh… the search line is for that fat32 partition. You can use UUID instead, of course, if you do not have labels. I always label all my partitions.