As of April 16, 2023, for anyone still having trouble finding maps, you may be having the same issue I was having, which no one else seems to have mentioned.
TLDR: Ensure that the character that originally looted [item=202081] has reached Dragonscale Expedition Renown 21.
You can check if the quest was completed on a specific character by running this script:
/script print(C_QuestLog.IsQuestFlaggedCompleted(72708))
The Rest: I swapped mains early on in the expansion, I started off as a Demon Hunter, then ended up switching to Evoker midway through Normal Vault of the Incarnates. Fast forward a few months and I'd been max renown on my Evoker for a long time, had looted hundreds and hundreds of dirt piles and expedition packs and had never seen a single map drop. Then I learned that [item=202081] is only usable once per account, but the effects of looting maps are supposed to be account-wide, so there isn't supposed to be a problem.
However, my Evoker had never completed it, my old Demon Hunter had. So I decided to test out a theory and levelled my Demon Hunters Dragonscale Expedition Renown to 21. Immediately after reaching Renown 21 on my Demon Hunter, I swapped to my Evoker and 2 Chests, 2 Packs and 13 Dirts later, I looted [item=198843] from a [object=383735] in Ohn'ahran Plains.