How do you recommend following up on action items?

The retrospective does not end when completed. In fact, now is the hardest part. Follow-up to the retroactive action plan. In retrospective, one of the results is an element of action that the team has identified to significantly improve the process or work environment (reflection can be started at different levels). If the action points identified in the previous retrospective are not processed or lost in the sprint process, the team will refrain from achieving the points as there is no final work on the item. Therefore, the Scrum Master needs to present action points for the final retrospective and discuss progress.

This gives the team the satisfaction that they are listening and being followed until the item is complete. There are several ways to track. For eg. Running the activity:

Open the list of action items (and their respective owners)
Update the status for each item on the list.
Add newly identified items

Each team can have a different tool for tracking their action items. Some examples: post-it on the team wall, a shared excel document, Trello, etc.