This problem has existed since the first time dogs were added; however, it has still never been fixed. If you use any mode of transportation for example a boat, nether portal, or elytra your tamed pet gets stuck in unloaded chunks and stops following you / teleporting to you. This makes using pets completely useless since you lose them the instant you try to travel anywhere. Pets should teleport to you no matter if they are in unloaded chunks or not. I do not see how this is an issue considering you can use the teleport command using cheats and they get teleported out of unloaded chunks. Please fix this so the new content is actually usable from the new update. Without this design issue being fixed there is no point in taming or using pets at all. Standing pets should always be loaded!

This is easily replicable. Use any mode of transportation to travel quickly (elytra, boat, sometimes horse) and any pets not teleported before the chunks are unloaded are frozen in place. In addition, pets cannot teleport while swimming or teleport into water. In addition if you enter a nether portal before your pet, your pet stays on the other side. The same is true for the end.