Canon 20Da has a Canon EF/EF-S lens mount and currently there are 333 native lenses available for this mount.
The latest released lenses that are compatible with the 20Da are the Samyang MF 14mm F2.8 Mk2, the Samyang MF 85mm F1.4 Mk2 and the Irix 45mm F1.4.
Canon 20Da doesn't have a sensor based image stabilization system but
114 of these lenses already comes with optical image stabilization.
Since Canon 20Da has a APS-C sensor, it has a focal length multiplier of 1.6× so you have to multiply lenses original focal length with this multiplier to find the Full Frame equivalent focal length of the lens when mounted on 20Da.
You may also also be interested in these:
Canon 20Da Lenses with Image Stabilization
Canon 20Da Lenses with Weather Sealings