Hi Ceres, apt pinning is possible but risky if you don't know first precisely what you're doing.
If you're not in a hurry, you can wait for a bookworm's backport of 0ad, it will come sooner or later.
If you're in a hurry, you may use the flatpack or snap packages of 0ad, which are up to date, until bookworm's backport of 0ad is ready.
It would be separated from the Debian packages if you want to compile yourself a version from the repository for testing purposes.