Companies like Sigma are known for creating relatively affordable third-party lenses for brands like Sony, Canon, Nikon, and so on. This is a great alternative for photographers who might find that first-party lenses are too expensive. However, given that these are third-party lenses, compatibility might be an issue.
In the case of Canon’s EOS R lineup, users had to rely on an adapter made by Canon, although in some instances, there are limitations. However, a report from Canon Rumors claims that based on what they’ve heard from their sources, apparently come 2022 Sigma will be releasing lenses that will work with the EOS R’s RF mount.