Adding a Subclass to an Actor Through Class Advancements does not add the Subclass's Advancement Features for that level

[CrimsonShiroe]

If you have an class with an advancement to add a subclass (for example, granting a Subclass item at level 3 for Artificer) does not give a prompt for accepting the subclass features for the level it was added (for example, the Alchemist level 3 features).

[MaxPat931]

There are plans to add a Subclass Advancement Type to address this #1407

The Advancement User Guide on the wiki mentions this as well https://github.com/foundryvtt/dnd5e/wiki/User-Guide#managing-subclasses