Hi,
I'm using Ubuntu Mate 20.04 LTS. Is possible to use Thunar instead of Caja to open folders and file managment?
Nothing change when:
Hello puff2000
You may find these video tutorials about Caja to be useful:
Hope that helps until you get your computer set up the way you want it. 
Have you installed thunar?
If not,
sudo apt install thunar
Then,
Preferred Applications, System, and File Manager.
As he mentioned in his start post he already did that.
Yes, you can use Thunar. I used to install it because thumbnails would not show on my HP laptops until I had opened them once in Thunar. I now have a System 76 laptop so no longer install Thunar, but it worked when I used it. Remember Thunar is different, it is not a clone of nautilus/mate. You will find the preferences and how it works somewhat different.
Very nice reminder.
I have always been quite happy with Caja and never really thought of using another file manager. But with the latest updates of 20.10, there appeared - very occasionally, I must say - small glitches on using it. Like not reading subfolders.
Nothing that a simple restart cannot solve.
So perhaps it makes sense to try and use Thunar for a while.
@puff2000, indeed there seems to be an issue.
To test, I changed preferred program to Thunar and just downloaded random stuff from internet. When download finishes, there is down-arrow indication for downloads, there we can choose to open the folder (open containing folder). When I click on it, what launches is Caja and not Thunar!
Edit: Just to be clear it is same issue even after logout-login as well as reboot.
P.S.: I'm on 21.04
I think you will enjoy Thunar.
It's custom actions are very useful.