With two different browsers (Chromium and Firefox), the identical problem arose simultaneously: Mirage is now opening instead of Dolphin. The file is neither displayed, nor is there any indication of where it is located.

Because two browsers were identically affected, at the same time, may I suspect this a KDE-setting problem, rather than a browser-setting problem?

If a mime setting has become corrupted, how would I find it? In Linux Mint's System Settings, one can only search by file extensions, but not by the names of programs that are affected. I have no idea which extension may have incorrect settings.

Or, is this not a mime problem, but something else?

Please let me know the best way to resolve this.

Never used Mint or Mirage but I see it is used for displaying various image types, I presume in the same way as Okular is in KDE.

I guess that Mirage has become the primary programme associated with whatever file types Chromium/Firefox are passing to it. (Looking at image types in my Neon installation I noted that several of them were set to open in Firefox as default - not any more!

Thanks, @Gummidge, for wanting to help me!

I did more searching through posts on related questions and solved the problem.

There was a "Application Preference Order" error in System Settings -> File Associations, and you have to look under 'inode/directory' to find it. Somehow, Mirage got to the top of the list.

If possible, I'll close this thread for others to find, with the same problem.

its a systemwide problem affecting KFind , firefox & waterfox too.
Usually Gnome gets you in this terrible mess. Do not install gvfs-mime or any of this breakware.

to fix it, follow the link and replace the Exec line with "Exec=/usr/bin/false" in any ****FileManager1.service file you find below /

https://polywogsys.livejournal.com/309405.html

quite bothersome mess-up, keep your system clean of any Gnome-ware.

https://support.mozilla.org/en-US/quest ... er-1233979

the best way is to saboatage Gnome like this: https://bugs.launchpad.net/ubuntu/+sour ... omments/74

Dolphin is packaged with

file:///usr/share/dbus-1/services/org.kde.dolphin.FileManager1.service

containing

[D-BUS Service]
Name=org.freedesktop.FileManager1
Exec=/usr/local/bin/dolphin --daemon

when you do a local compile of the Dolphin sources and build with ninja, a second such file will be installed under

/usr/local/share/dbus-1/services/

this causes trouble with breakage of KDevelop (open project setting) and KFind and Firefox ("open containing folder" and mark the downloaded file therein) which will not work.

to fix this , remove the superfluous /usr/local/share/dbus-1/services/org.kde.dolphin.FileManager1.service

or change the exec line to
Exec=/usr/bin/false