PubMed released a summary of their nationwide residential radon survey. Analyzing data from the radon surveys in 21,818 Canadian homes, they found an average radon concentration of 82 Bq m^3, with soil being the primary entry point. Houses with basements have double the radon levels compared to those without, and those with private wells also tend to have higher levels.
You can find the full release here: https://pubmed.ncbi.nlm.nih.gov/34570051/