Very quick:
- Install latest Wine-Version
- Install Lutris
- Download Project Landsword
- Extract the ZIP-File
- In Lutris add a new game from local files
- Choose Wine as starter (Info-Tab)
- Choose the extracted .exe as executable (Settings-Tab)
- Choose your extracted folder as Working Directory (Settings-Tab)
- Choose "GE-Proton (latest)" as Wine-Version (Options-Tab)
- Save and Have Fun!
It's possible that you have to start and cancel it twice or more. But after that it should run with one try.