UPDATED 4/27:
As things stand right now...
70 Cubs minor leaguers are eligible for selection in the December 2021 MLB Rule 5 Draft, and 44 Cubs minor leaguers (39 post-2021 6YFA and five 2021 second-contract players) are eligible to be declared 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, RHP Pedro Strop (has Article XIX-A status) and INF Ildemaro Vargas (has Article XX-D status) accepted an Outright Assignment to the minors and deferred free-agency until the day after the conclusion of the MLB regular season, unless the player is added back to the MLB 40-man roster prior to filing for free-agency.