This appears to be a transient mirror synchronization issue on apt.postgresql.org. The Release file and Packages file were temporarily out of sync, which APT correctly rejected. Retrying after mirrors finish syncing should resolve the issue. No PostgreSQL packaging or server bug is involved.
sudo curl -o /usr/share/postgresql-common/pgdg/apt.postgresql.org.asc --fail https://www.postgresql.org/media/keys/ACCC4CF8.asc % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 100 4812 100 4812 0 0 14252 0 --:--:-- --:--:-- --:--:-- 14236
cat /etc/apt/sources.list.d/pgdg.sources Types: deb URIs: https://apt.postgresql.org/pub/repos/apt Suites: trixie-pgdg Components: main Architectures: amd64 Signed-By: /usr/share/postgresql-common/pgdg/apt.postgresql.org.asc