The Dragonflight pre-patch event can be used for leveling and is available to characters level 10 and above.

The intro questline appeared for an Allied Race character at Level 10. It didn’t pop up for a Level 1 character, so I assume the minimum level to participate in the event is 10. Horde players must talk to Ebyssian in Orgrimmar, and Alliance players to Wrathion in Stormwind.

You will also receive a Bronze Dragon flying mount to complete the intro questline.

However, you won’t be able to queue up for Uldaman, Legacy of Tyr, and complete the associated quest because it requires Level 60.

The catch-up gear does not scale with lower levels; equipping it requires Level 60.