On the Internet site of Tourism Ascona-Locarno there is a very good overview of all categories under the heading "Where to stay".
You can find it here: Tourism Ascona-Locarno
Click on the square with the 3 lines at the top right of this page and choose "Where to stay".
It is best to select "Ascona and surroundings" or "Locarno and surroundings" or "Tenero and surroundings" as the zone.
Note that very comprehensive PDF lists are also available for download.