Thanks everyone for the replies, so very happy to hear FAA is hosting chart services! This info exchange is a classic example of when the Esri Community forums are invaluable. Perhaps someone with existing posting capability can post in that pilotsofamerica forum mentioned earlier to let them know about the FAA service options for anyone that that was using Chartbundle's now defunct service? And for the record, below are links to the ArcGIS Online (AGOL) items/descriptions for the FAA services, and a graphic showing how I discovered them there. Per their AGOL item descriptions, sounds like they're being actively updated. And if anyone from FAA is reading this, those services really should be more formally titled than simply "VFR_Sectional" for example and marked "Authoritative" in ArcGIS Online (since FAA is hosting them) to make them easier to find - when I was trying to add them to an existing ArcGIS Online web map, I found the easiest way was to find them from the Browse/Add Data dialog was using the layer ID string. And I didn't see mention of these services on the FAA VFR Raster Charts page, so noting the availability of the services there would also be useful.
VFR Sectionals
https://faa.maps.arcgis.com/home/item.html?id=6ab79dc5de5743adb3e3b6e3c803aa59
VFR Terminal Area Charts (TACs)
https://faa.maps.arcgis.com/home/item.html?id=ba711890a6f24720bf63a77c5aeb1e64
IFR Enroute Low
https://faa.maps.arcgis.com/home/item.html?id=97ab03c55bb442b897daeba53a5cc85d
IFR Enroute High
https://faa.maps.arcgis.com/home/item.html?id=0cb4491ce486481e9d81de2234b13332
