It is hard to set Pluma as default application to open desktop-files

[Norbert]

Steps to reproduce:
1. Copy some desktop-file to the home folder with

    cp /usr/share/applications/firefox.desktop ~

2. Open Caja in home folder
3. Make right mouse click on newly copied firefox.desktop file, ensure that you have two options here - "Open With LibreOffice Writer" and "Open With Other Application"
4. Click on "Open With Other Application", select Pluma in the opened window
5. Repeat step 3 to see Pluma in the list

Expected results:
* desktop-files are now open with Pluma

Actual results:
* Pluma is not shown, "Open With LibreOffice Writer" stays in place

Workaround:

1. Hit Properties, go to Open With tab and repeatedly click on Remove button, then close this window.
2. Visit "Open With Other Application" and type `pluma` in "Use a custom command" and click Add (if does not work - do this twice)

ProblemType: Bug
DistroRelease: Ubuntu 21.04
Package: caja 1.24.1-0ubuntu1
ProcVersionSignature: Ubuntu 5.11.0-16.17-generic 5.11.12
Uname: Linux 5.11.0-16-generic x86_64
ApportVersion: 2.20.11-0ubuntu65
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: MATE
Date: Sat May 22 23:24:54 2021
InstallationDate: Installed on 2021-04-23 (29 days ago)
InstallationMedia: Ubuntu-MATE 21.04 "Hirsute Hippo" - Release amd64 (20210420)
SourcePackage: caja
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Bill Miller (wbmilleriii)]

The weird thing is, after doing this, there is an additional "pluma" in the Properties/Open With list. It appears that for some reason "Pluma" is forbidden from being the default application to open these files with, but you can get it to work with "pluma".

[Aex Rauch (centaurie)]

this is general in Mate. Same on debian (stretch) matedesktop.

xdg-mime query default application/x-desktop
userapp-pluma-JPST30.desktop

this desktop file appears under $HOME/.local/share/applications/

cat .local/share/applications/userapp-pluma-JPST30.desktop
[Desktop Entry]
Encoding=UTF-8
Version=1.0
Type=Application
NoDisplay=true
Exec=pluma %f
Name=pluma
Comment=Benutzerdefinition für pluma
alex@Taomon:~$

even with xdg-mime itself I can not change it to pluma.desktop