Can I open a 2019 drawing in an older version of sketch up?
Make note of the save options dropdown in the “save as” menu. Save it to the version you want it to open in.
The answer to your question was No on Mac, and Yes on Windows using an extension.
Save As would solve the problem if you have 2019.
No, lower versions can not open higher saved SketchUp files.
You can upload a received file to Trimble connect and save a 2017 version of the file (Make 2017 desktop is still available)
Or upload to 3D warehouse, and download from there.
Or use the warehouse…
The real point being, can I open files without paying?