UPDATED 1/6:
As things stand right now...
80 Cubs minor leaguers are eligible for selection in the December 2021 MLB Rule 5 Draft, and 40 Cubs minor leaguers (36 post-2021 6YFA and four 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).
Among the Cubs first-time Rule 5 Draft eligibles post-2021 are: RHPs Riley Thompson, Cam Sanders, Jeremiah Estrada, Ethan Roberts, Yovanny Cruz, Manuel Espinoza, Eduarniel Nunez, Benjamin Rodriguez, Luis Devers, and Kelvin Feliz, LHP Jack Patterson, C Jonathan Soto, 1B-OF Alfonso Rivas, INFs Luis Verdugo, Fabian Pertuz, Andy Weber, Luis Vazquez, Widimer Joaquin, Oswaldo Pina, Josue Huma, and Rochest Cruz, and OFs Nelson Velazquez and Edmond Americaan.