postgresql-17 on debian bookworm - directories missing

Hi there,
i have a debian bookworm with postgresql-16 installed, from postgresql
repository. I wanted to install postgresql-17 and then do a an inplace
upgrade via pg_upgrade.

Install: apt install postgresql-17 postgresql-17-postgis-3
postgresql-17-postgis-3-scripts postgresql-client-17

But after the installation there's no v17 cluster:

pg_lsclusters
Ver Cluster Port Status Owner Data directory Log file
16 main 5432 online postgres /var/lib/postgresql/16/main
/var/log/postgresql/postgresql-16-main.log

and these directories are missing:
/etc/postgresql/17/
/var/lib/postgresql/17/

Same happens when i try to install postgresql-18.

Am i doing smth wrong? Did i miss anything?

Thx,
Hubert