Newest and most sold lawnmower game this year got small update: https://store.steampowered.com/app/1346980/Lawnmower_Game_Next_Generation/
Also new totally different lawnmower game coming beginning of November, race themed lawnmower game, with lot of tracks. Store page live: https://store.steampowered.com/app/1433890/Lawnmower_Game_Racing/