Finally "system reconfigure"d with your patch.

The first entry fails to boot with:

--8<---------------cut here---------------start------------->8---
loading kernel modules...
ice-9/boot-9.scm:1669:16: In procedure raise-exception:
In procedure string-prefix?: Wrong type argument in position 2
(expecting string): #<file-system-label "guix">
--8<---------------cut here---------------end--------------->8---

Funny thing is, the previous generation boots properly!

My config.scm's filesystem layout:

--8<---------------cut here---------------start------------->8---
(file-systems (cons* (file-system
                         (device (file-system-label "guix"))
                         (mount-point "/")
                         (type "btrfs")
                         (options "subvol=rootfs,compress=zstd"))
                       (file-system
                         (device (file-system-label "data"))
                         (mount-point "/media/data")
                         (type "ext4"))
                       (file-system
                         (mount-point "/tmp")
                         (device "none")
                         (type "tmpfs")
                         (check? #f))
                       %base-file-systems))
--8<---------------cut here---------------end--------------->8---

-- 
Pierre Neidhardt
https://ambrevar.xyz/