guix describe:

Generation 23   jul 06 2023 13:37:00    (current)
  guix 2426e51
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 2426e51688d479042ea115a634c6be2d8b9f3b99

It appears that harfbuzz has been duplicated using the same version, so when creating

a shell with guix shell harfbuzz it will show a warning about an ambiguous specification:

guix shell harfbuzz
guix shell: warning: ambiguous package specification `harfbuzz'
guix shell: warning: choosing harfbuzz@5.3.1 from gnu/packages/gtk.scm:252:2

It may be as simple as removing harfbuzz-5 package definition but I'm not sure if that is correct,

or if this is intended.