Is there a way to force all documents to open as read-only by default?

We recently migrated a ton of documents to SharePoint and users are having a hard time with AutoSave.

We're looking to see if it's possible to make all documents open as read-only by default, to force users to opt in to editing. We're hoping to avoid accidental changes.

We decided to disable AutoSave by default, but that's creating other issues where users are seeing outdated versions of files that others have also edited.