Entities with passengers cannot use Nether Portals, End Portals and End Gateways to teleport. In Java Edition snapshot 24w21a the entitiesWithPassengersCanUsePortals gamerule was added. When true, entities with passengers can use Nether Portals, End Portals and End Gateways, however it defaults to false.

Steps to reproduce:

1. Create a portal
2. Spawn a boat or a jockey
3. Push the ridden/Ride the entity into the portal

Observed results:
The entities with passengers cannot travel through the portals

Expected behavior:
The entities with passengers would be able to travel through the portals