The legality of recording the space itself is not usually the issue; disclosure is. A doorbell camera at the entrance and an interior camera monitoring the whole showing are treated the same way under those disclosure expectations, even though buyers often notice only the obvious one at the door.
Audio recording carries an extra layer of sensitivity, since a private conversation between a buyer and their agent inside the home touches on more than security, which is exactly why disclosure matters before you walk through, not after.
If you are shown a home and were not told a camera was present, raise it with your own agent right away, especially on a higher-value home near or above the Saskatoon benchmark of $444,700. Get your hand-reviewed valuation from Joel Dyck.