This apply only to KDE apps, IDK why and I am not so sure what I suppose to search for so if anyone know a keyword I should look at (or even better, how to solve this) please point it out for me.
WM : i3
Have you tested some other file manager’s Open with?
Maybe it’s file manager
I tried on Pcmanfm and it displayed correctly. So I guess it’s on Thunar. Thanks for the advice 
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If somebody won’t come up with why it happens, check out their upstream tracker, maybe it worth reporting 
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OK, so I search for this specific problem to no avail. So I guess I’ll wait and see if someone in this forum has any idea before report it to XFCE guys.
NVM, I think I found the reason
[pannxe@x510uf ~]$ ls /usr/share/applications
akm.desktop krita_spriter.desktop org.kde.mobile.okular_fax.desktop
anki.desktop krita_svg.desktop org.kde.mobile.okular_fb.desktop
arandr.desktop krita_tga.desktop org.kde.mobile.okular_ghostview.desktop
avahi-discover.desktop krita_tiff.desktop org.kde.mobile.okular_kimgio.desktop
blueberry.desktop krita_xcf.desktop org.kde.mobile.okular_md.desktop
bluetooth-sendto.desktop ktelnetservice5.desktop org.kde.mobile.okular_mobi.desktop
bssh.desktop kvantummanager.desktop org.kde.mobile.okular_pdf.desktop
bvnc.desktop lightdm-gtk-greeter-settings.desktop org.kde.mobile.okular_plucker.desktop
chromium.desktop lstopo.desktop org.kde.mobile.okular_tiff.desktop
cmake-gui.desktop lxappearance.desktop org.kde.mobile.okular_txt.desktop
com.github.themix_project.Oomox.desktop mimeinfo.cache org.kde.mobile.okular_xps.desktop
com.obsproject.Studio.desktop mplayer.desktop org.kde.okular.desktop
compton.desktop nitrogen.desktop org.qutebrowser.qutebrowser.desktop
cups.desktop nm-applet.desktop paprefs.desktop
electron.desktop nm-connection-editor.desktop pavucontrol.desktop
eos-log-tool.desktop nnn.desktop picom.desktop
eos-update-notifier-configure.desktop nvidia-settings.desktop polkit-gnome-authentication-agent-1.desktop
feh.desktop okularApplication_chm.desktop qv4l2.desktop
galculator.desktop okularApplication_comicbook.desktop qvidcap.desktop
gcr-prompter.desktop okularApplication_djvu.desktop reflector-simple.desktop
gcr-viewer.desktop okularApplication_dvi.desktop ristretto.desktop
gkbd-keyboard-display.desktop okularApplication_epub.desktop signon-ui.desktop
gtk3-demo.desktop okularApplication_fax.desktop spotify.desktop
gtk3-icon-browser.desktop okularApplication_fb.desktop stoken-gui.desktop
gtk3-widget-factory.desktop okularApplication_ghostview.desktop stoken-gui-small.desktop
gufw.desktop okularApplication_kimgio.desktop system-config-printer.desktop
hardinfo.desktop okularApplication_md.desktop thunar-bulk-rename.desktop
htop.desktop okularApplication_mobi.desktop thunar.desktop
i3.desktop okularApplication_pdf.desktop thunar-settings.desktop
krita_brush.desktop okularApplication_plucker.desktop thunar-volman-settings.desktop
krita_csv.desktop okularApplication_tiff.desktop UpdateInTerminal.desktop
krita_exr.desktop okularApplication_txt.desktop uxterm.desktop
krita_gif.desktop okularApplication_xps.desktop visual-studio-code.desktop
krita_heif.desktop org.fontforge.FontForge.desktop visual-studio-code-url-handler.desktop
krita_heightmap.desktop org.gnome.FileRoller.desktop vlc.desktop
krita_jp2.desktop org.gnome.seahorse.Application.desktop welcome.desktop
krita_jpeg.desktop org.inkscape.Inkscape.desktop xed.desktop
krita_kra.desktop org.kde.kded5.desktop xfce4-about.desktop
krita_ora.desktop org.kde.krita.desktop xfce4-terminal.desktop
krita_pdf.desktop org.kde.mobile.okular_chm.desktop xfce4-terminal-settings.desktop
krita_png.desktop org.kde.mobile.okular_comicbook.desktop xterm.desktop
krita_psd.desktop org.kde.mobile.okular_djvu.desktop yad-icon-browser.desktop
krita_qimageio.desktop org.kde.mobile.okular_dvi.desktop Zoom.desktop
krita_raw.desktop org.kde.mobile.okular_epub.desktop
There are many duplication of those KDE apps. Now the question become: Is it safe to delete them.
No it’s actually was quite some time like that, so…
They use this stupid technique with .desktop per program mime associacion
Thunar for some reason just decided to ignore it this time 
That’s unfortunate. 
this is indeed a very strange way and it looks like they need this under plasma itself ? every entry have this MimeType=image:xyz inside…
I would think that this is also not following the freedesktop specifications… there is the option for desktop files to “only show in kde”
OnlyShowIn=KDE;