You have to add the ceph repository:
PVE Server -> Updates -Repositories -> Add: Repository -> Ceph no-subscription
But WHY are you installing Proxmox 7, the version you should use is 8 (8.1 to be precise)
Code:
apt update; apt full-upgrade
Check for potential problems with
pve7to8
apt-get install -y rename gpgv
# Eintrage in /etc/apt/sources.list(.d) updaten
sed -i 's/httpredir/deb/g' /etc/apt/sources.list
sed -i 's/httpredir/deb/g' /etc/apt/sources.list.d/*.list /etc/apt/sources.list.d/*.sources
sed -i 's/bookworm/trixie/g' /etc/apt/sources.list
sed -i 's/bookworm/trixie/g' /etc/apt/sources.list.d/*.list /etc/apt/sources.list.d/*.sources
sed -i 's#bullseye/updates#bookworm-security#g' /etc/apt/sources.list
sed -i 's/bullseye/bookworm/g' /etc/apt/sources.list
sed -i 's#bullseye/updates#bookworm-security#g' /etc/apt/sources.list.d/*.list /etc/apt/sources.list.d/*.sources
sed -i 's/bullseye/bookworm/g' /etc/apt/sources.list.d/*.list /etc/apt/sources.list.d/*.sources
sed -i '/backports/s/^/#/g' /etc/apt/sources.list /etc/apt/sources.list.d/*.list /etc/apt/sources.list.d/*.sources
cd /etc/apt/sources.list.d/
rename 's/bookworm/trixie/g' *
rename 's/bullseye/bookworm/g' *
sed -i 's/bookworm/trixie/g' /etc/apt/preferences
sed -i 's/bookworm/trixie/g' /etc/apt/preferences.d/*
sed -i 's/bullseye/bookworm/g' /etc/apt/preferences
sed -i 's/bullseye/bookworm/g' /etc/apt/preferences.d/*
cd /etc/apt/preferences.d/
rename 's/bookworm/trixie/g' *
rename 's/bullseye/bookworm/g' *
egrep -lris 'non-free$' /etc/apt/sources.list* | xargs -r sed -i 's/non-free$/non-free non-free-firmware/'
if [ -e /etc/apt/sources.list.d/extrepo_proxmox-pve.sources ] || [ -e /etc/apt/sources.list.d/extrepo_proxmox-pbs.sources ]; then
wget -O/etc/apt/trusted.gpg.d/proxmox-release-bookworm.gpg
https://enterprise.proxmox.com/debian/proxmox-release-bookworm.gpg
sed -i 's#^Signed-By:.*#Signed-By: /etc/apt/trusted.gpg.d/proxmox-release-bookworm.gpg#' /etc/apt/sources.list.d/extrepo_proxmox-*.sources
apt update
fi
apt-get update
apt -y -d upgrade; apt -y -d full-upgrade
apt upgrade --without-new-pkgs
apt full-upgrade
# Auf Proxmox (mindestens) kann ntpsec Probleme machen
if [ 0 -lt $(dpkg -la | awk '$2 == "ntpsec"' | wc -l ) ]; then
apt install chrony
fi
apt autoremove
reboot
