Created attachment 164159 [details]
Unmodified report from kcrash, which remained on "sending" for over 30 minutes. It includes the backtrace at the end

SUMMARY
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(Attaching unmodified report from kcrash, which failed to send. It includes the backtrace at the end)

STEPS TO REPRODUCE
1. From Dolphin, right click* on a .lml file
2. Select Open With... > LabPlot2**

*if I left-click on it, Ark opens it instead of Labplot2
**On the "Choose Application" dialog, LabPlot2 appears twice: under Education > Science and under Education > Mathematics. Both entries produce the same result

OBSERVED RESULT
The banner from LabPlot2 appears, but the program does not open and the "Program crashed" notification appears.

Opening LabPlot2 first, and then opening the file from it, works without issues.
The file is in a mounted drive outside of /home/, and was created by the same version of LabPlot2 on the previous day.


EXPECTED RESULT
LabPlot2 should open the file without crashing

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Linux 5.4.0-150-generic x86_64
Distribution: Ubuntu 18.04.6 LTS
KDE Plasma Version: 5.12.9
KDE Frameworks Version: 5.44.0
Qt Version: 5.9.5

ADDITIONAL INFORMATION
- Custom settings of the application:
- Preferences > General > Startup is set to "Do Nothing" (this was set by default).
- Only setting I remember changing is: moving the CartesianPlot toolbar to the left side, and changing it from "Text Position > Icons Only" to a different setting, and back to "Icons Only" (because it was initially displaying text despite being set to "Icons Only").
- However, settings may have been imported automatically from a newer app version (see the last paragraph)
- Plasma added (years ago) after OS install, to have it alongside GNOME (loaded environment is user-dependent). Bug happened on Plasma. Did not try on GNOME.

- Before installation, I installed the 2.10.0 snap version, but was unable to save anything to ~/Documents, nor to a mounted drive (also, CAS notebooks did not appear anywhere except for their tab in "Preferences". Not even the "configure CAS" entry appeared in "Settings", although later points show traces of CAS-related tools), so I uninstalled it and went for the (outdated but functional) regular version.
- All installations and the uninstallation were done through Discover.
- Rebooted after installing 2.10 snap (to try to solve inability to save), but did not reboot between uninstalling 2.10 snap and installing 2.4 "regular" version.
- App (2.4) shows the modern ("blackboard") icon on the computer, despite Discover showing the older ("greenboard") icon for it . May be related to snap version having been installed before.
- Regarding the previous point, "Configure Toolbars" seems not to show all toolbars, and has a "CAS Worksheet <LabPlot>" toolbar entry (despite Notebooks not being on this version). "Configure Shortcuts" also has a "CAS Worksheet" entry (assigning a combination to it and pressing it did nothing), so config may have been kept from snap 2.10 version (is that possible?). Restoring Preferences, toolbar settings and shortcut settings to default configuration did not revert the situation. However, "Settings > Toolbars shown" does not show this "CAS Worksheet <LabPlot>" entry, and does show all (existing) toolbars.
- I believe that I had never installed LabPlot2 on this system before installing the 2.10 snap.

The crash can be reproduced every time.