DND 5e could easily adopt a version of the Simple Skills DC (no level) table from Pathfinder 2e* along with the DC adjustments table**; that would be an excellent starting point for DCs and being able to adjust them to account for proficiency or not.
* DC increasing in steps of 5 - 10, 15, 20, 25, 30. This corresponds to Pathfinder 2e's proficiency scaling - Untrained, Trained, Expert, Master, Legendary (0, 2, 4, 6, 8 proficiency bonus to a skill).
** The numbers are still very different in Pathfinder 2e, along with proficiency; so I'm not sure how useful the default DC adjustment table will be - that goes in steps from 2 to 5 to 10, negative and positive, from incredibly easy to incredibly hard. Perhaps for 5e, adjustments of 1 to 3 to 5 would be most appropriate.