An error occurred while saving the commentLouis McCarthy commented
Yes, you can use the SharePoint side to change it:
Go to Files tab in teams and click on any file's ellipsis hot area
Select "Open in SharePoint"
Wait a few seconds for it to open in a browser window
Click on the file in the SharePoint browser window
Click on the "Manage access" URL
Click on the team "[team-name] Members" upside down caret hot area
Select "Can view" instead of the "Can edit"
Boy, it would be so much simpler if there was a "Set to read-only" in teams...
Still under review by the feature team. Nothing new to report at this time.