If you are using Steam, right-click Stardew Valley > > Updates > Set to "Only update this game when I launch it." Then, always launch via the .exe in the folder, not the Steam Play button.
The Stardew Modding API (SMAPI) updates slower than the main game. When Stardew Valley 1.6 launched, thousands of mods broke. If you have a massive mod list for 1.5 (like Stardew Valley Expanded older versions), you need to roll back your game to to keep playing until mod authors update. stardew valley compatibility version download link
Steam will automatically download the legacy 32-bit version. Stardew Valley 2. GOG Galaxy Instructions Owned Games list, right-click Stardew Valley Manage Installation Beta Channels drop-down menu and choose "Compatibility" The game will update to the 32-bit version. 3. Advanced: Manual Depot Download (Steam Only) For specific use cases like PortMaster If you are using Steam, right-click Stardew Valley