My guess is, that there is a problem with postgresql-old-upgrade. If the new packages ar installed earlier than running postgresql-old-upgrade, there is a mess with the old-datadir:
Actual major version is 15, I guess @gigi314 is running 14, so he has
old-datadir=/…/data13
The update makes it
old-datadir=/…/data14
and after that $ pg_upgrade --check claims an error.
Therefore I delay the packages
#delay PostgreSQL for pg_upgrade
IgnorePkg = postgresql
IgnorePkg = postgresql-libs
IgnorePkg = postgresql-old-upgrade