From what I read in the report, The OEM floated the idea of synthetic airspeed for the Max but realized quickly that due to “new & novel” language in Part 25 Cert rules, this would delay the cert and jeopardize their plan of “minimal training differences (Level B) between NG and Max.
The ADIRUs provide HDG/Groundspeed display to the ISDU on the overhead. Not stated in the NNC for Unreliable Airspeed explicitly, but this could be useful information if the pilots know where to find it and how it is determined.