I recently returned and rolled an allied character (Maghar Orc) and then got the opportunity to start at lvl 10. I started with “Old world” content (so ignoring Chromie and the Warchief board), but I was not able to select Ragefire Chasm in the dungeon finder, for example. Instead, my only option was the first BfA dungeon. It also seems that professions are preselected for Cataclysm, which makes no sense to me. Have I overlooked something?
I think you need to do the BFA story leveling first if you havent done it before. The second time you level you can select from chromie where you wanna go to level.
If you want to do the original levelling through Kalimdor and EK, you need to go to Chromie and select Cataclysm. Original quests are all considered as part of the Cataclysm timeline.
As far as I know, the classic dungeons should then be on your list. If you don’t talk to Chrmie, you are by default in the BfA timeline, and are offered BfA dungeons.
Edit:
I am thinking that if Croydon was able to roll a Mag’yar Orc, Chromie should be available. If not, at least he will find out, and we can deal with that.
I have read a case here somewhere where people can use Chromie Time after just doing the intro to Boralus.