UPDATED 8/14:
As things stand right now...
60 Cubs minor leaguers are eligible for selection in the December 2021 MLB Rule 5 Draft, and 49 Cubs minor leaguers (33 post-2021 6YFA and 16 2021 second-contract players) are eligible to be declared MLB Rule 9 (formerly known as MLB Rule 55) minor league 6YFA at 5 PM Eastern on the 5th day after the final game of the 2021 World Series (or at 5 PM Eastern on October 15th if the 2021 World Series is cancelled).
In addition, OF Nick Martini and LHP Kyle Ryan were assigned outright to the minors (Martini on on 6/7 and Ryan on 9/14), and because they have Article XX-D status (both Martini and Ryan have been outrighted previously in their careers) they had the right to elect free-agency, or else defer the right to elect free-agency until after the conclusion of the MLB regular season (he had 48 hours to decide).