Recently installed Ubuntu Mate 20.4 and have been very pleased except for one thing. I store my files on a Synology NAS and in Caja .doc files show as unknown type. This seems to be a new issue with Ubuntu Mate 20.4 and also with Mint 20. Did not have this problem with 18.4 or several previous versions of Mint.
When I click on a doc file in Caja it tries to open with an unrelated program. When I right click on the file Libre Office Writer is not an option. I can go to "Open Other Application" and select Writer (making sure to check the remember box) and the file opens fine. Next time I try a doc file it is the same problem over again. So right click on file, click properties, click "Open With". No applications listed. Try to "Add" Writer, it will not add it to applications.
I should note at this point that if I drag a doc file to my Desktop, type shows as Microsoft Word Document and opens just fine in Write.
Now, I happened to also have Thunar installed so started playing around with that. Same issue when clicking on a doc file on the NAS. Then I right clicked on a doc file, changed "Open With" to Writer. Now when I click on a doc file in either Caja or Thunar it opens with Writer. However doc files on the NAS still show unknown file type.
Any one have any thoughts on this issue?