Files with no checked in version - force check in using CSOM

User added 2k+ files to a document library, but did not check them in and is no longer at the firm.

Using the library setting: 'Manage files which have no checked in version' I can list the files, but checking all and taking ownership returns an error. Checking the files individually and taking ownership in smaller batches does work, just time consuming. For the next time this occurs as well as to find others that were never checked in-

Is there a method in the CSOM to return these files and take ownership?

There are a number of articles/powershell examples on doing this with SharePoint on-premise, using list.CheckedOutFiles, but I have not found a comparable method in the CSOM. Is there one?