Trial spawners don't work for existing Snapshot Java Realms worlds

When playing in a world that was created in a Java Realm with the Update 1.21 experiment applied, before version 23w45a, naturally generated trial spawners in trial chambers are deactivated and do not spawn any mobs. Image provided.

Trial spawners also do not spawn any mobs even when using a mob spawn egg on them, both in Survival and Creative modes.