Cyan games that are 64-bit compliant with MacOS from Catalina to present:

Obduction
realMyst: Masterpiece Edition
Myst III: Exile
Riven: The Sequel to Myst
Myst: Masterpiece Edition

Cyan games that are not yet 64-bit compliant with MacOS from Catalina to present:

 
URU: Complete Chronicles
Myst V: End of Ages
Myst IV: Revelation

Note: Cyan is working with Codeweavers, the developers who helped us update the games in 2018, to make the games compliant with Apple's latest update requirements. 

There is no ETA for when the update process will be complete. Thank you for your patience. 

Please also review this FAQ entry