For this discussion, MY20 would be ‘L’ series ACM modules. I believe that most if not all MY20 ACM’s have different connectors than the MY19 and earlier units. You can use an MY20 ACM in previous year vehicles, but you will need to rewire or replace the connectors as well as reprogram a few things in the asbuilt.
The A2B protocol/connector thing is not an issue. This is an additional connection that was added to provide a digital connection to the new amplifiers from B&O, Revel, etc. Provided that the ACM is programmed correctly, you can still use the analog connections for the previous generation of amplifiers like Sony, Kicker, etc. This connection and the implementation is largely misunderstood.
EDIT: I recently looked at a MY2021 ACM asbuilt database and found that the new ACM’s have the ability to turn off the A2B function completely. This consistent with asbuilt settings for the 2018+ ACM’s.
I have a late model MY19 ACM in my 2015 F150 Platinum with the Sony system. The MY19 ACM still has the previous connectors, so minor rewiring adding the SDL links. The reason I changed it was to gain access to the new SiriusXM tuners to improve the SiriusXM performance and expanded channels. It required some additional wiring for the SDL (Satellite Data Links) between the ACM and APIM. This information is included here:
2020 APIM/Screen and 2020 ACM Compatibility - Ford / Hardware - CyanLabs Official Community
The ACM I used does not have HD Radio so I can’t speak to the HD Radio 'Artist’s Experience".
This excellent thread by DanMc85 might help with your model year…
Variable Line Level Preamp Outputs From ACM (Factory Radio) For Amplifier Upgrades (2gfusions.net)