https://bugs.winehq.org/show_bug.cgi?id=55256
--- Comment #15 from jkfloris@dds.nl --- Yeah, I just thought of that too, but unfortunately it was too late.
On the Wine forum I can find one user who has/had the same problem, and Google also gives only two hits, neither of which is clear what the problem was. It looks like that after adding the .sources file, "apt update" was not performed.