Unable to sort 'activity history' enhanced related list

The Product Team has confirmed that this is a known limitation and working as designed.

This limitation specific to the 'Open Activities' and 'Activity History' related lists.

Alternatively, Instead of relying on the "Activity History" and "Open Activities" related lists, you can use the Activity Timeline component, which provides a more comprehensive view of activities. 

Please consider creating or promoting the Idea: Allow Sort Ability for Columns on Enhanced Related Lists in Lightning so the larger Salesforce Trailblazer Community can vote on expanding enhanced related lists availability to these related lists via a future release.