in general though, a uki bundles in the cmdline, it would require a fundamental change to how things currently work in bazzite, we wouldn't need grub anymore since efibootmgr would be in charge of registering ukis with efi boot entries
so on update, when everything is generated, the uki blob gets created, and then registered with efi, but again, would require a substantial and fundamental change, nothing at all with how bazzite updates work atm
i remember trying to make refind work with endeavouros, got as far as making a hook so that on kernel upgrades i can generate a boot stanza, i ended up abandoning it and hiding systemd-boot behind plymouth lol