Several apps seem to not be launchable by krunner, KDE shortcut, or .desktop file, unless they redirect stdout. I have no idea if this is the fault of the apps or KDE or something else, but I report here in case it's the place.

Three examples:

If I start stellarium from the command line it works fine:

$ /path/to/Stellarium-25.1-qt5-x86_64.AppImage

If I start OBS from the command line it works fine:

$ flatpak run com.obsproject.Studio

If I start qjackctl from the command line it works fine:

$ qjackctl

However if I make these .desktop files in ~/.local/share/applications/ :

[Desktop Entry]
Name=stellarium
Exec=/f2/sr/sa/Stellarium-25.1-qt5-x86_64.AppImage %F
Type=Application
Categories=

[Desktop Entry]
Name=obs
Exec=flatpak run com.obsproject.Studio %F
Type=Application
Categories=

...or I make this script in ~/bin:

#!/bin/bash
qjackctl

...and then I start any of them with krunner, or I assign a KDE shortcut to them, they do not start.

*** HOWEVER, if I redirect their stdout somewhere, such as:

Exec=/f2/sr/sa/Stellarium-25.1-qt5-x86_64.AppImage %F > /dev/null

or

#!/bin/bash
qjackctl > tmp/qjackctl.log

...then they all work fine.

If stdout is not redirected, they all fail in different ways. For obs, journal looks like this:

Jul 22 13:11:38 mycomputer systemd[1644]: Started app-obs-f78fa17390e84c6b805861ca24b08f36.scope - obs-usethis.
Jul 22 13:11:38 mycomputer systemd[1644]: Started app-flatpak-com.obsproject.Studio-261160.scope.
Jul 22 13:11:38 mycomputer kwin_wayland_wrapper[261171]: warning: queue 0x5625c412bd60 destroyed while proxies still attached:
Jul 22 13:11:38 mycomputer kwin_wayland_wrapper[261171]:   wl_registry@36 still attached
Jul 22 13:11:41 mycomputer xdg-desktop-portal-kde[2655]: xdp-kde-settings: Key  "menuFont"  doesn't exist
Jul 22 13:11:41 mycomputer xdg-desktop-portal-kde[2655]: xdp-kde-settings: Key  "font"  doesn't exist
Jul 22 13:11:41 mycomputer xdg-desktop-portal-kde[2655]: xdp-kde-settings: Key  "activeFont"  doesn't exist
Jul 22 13:11:41 mycomputer xdg-desktop-portal-kde[2655]: xdp-kde-settings: Key  "toolBarFont"  doesn't exist
Jul 22 13:11:41 mycomputer xdg-desktop-portal-kde[2655]: xdp-kde-settings: Key  "smallestReadableFont"  doesn't exist

For stellarium:

Jul 22 13:13:08 mycomputer kwin_wayland_wrapper[263787]: open dir error: No such file or directory
Jul 22 13:13:08 mycomputer kernel: Stellarium-25.1[263790]: segfault at 8 ip 0000000000409442 sp 00007ffe5a06afe0 error 4 in Stellarium-25.1-qt5-x86_64.AppImage[405000+1d000] likely on CPU 6 (core 6, socket 0)
Jul 22 13:13:08 mycomputer kernel: Code: 8b 45 f4 eb 13 48 8b 45 f8 48 8b 10 48 8b 45 c8 48 89 10 b8 00 00 00 00 c9 c3 55 48 89 e5 48 83 ec 10 48 89 7d f8 48 8b 45 f8 <48> 8b 40 08 48 89 c7 e8 f2 bb ff ff 48 8b 45 f8 48 89 c7 e8 e6 bb
Jul 22 13:13:08 mycomputer systemd[1644]: app-stellarium-9969da1a5c0c472eaafd7801c4c84b28.scope: Couldn't move process 263787 to requested cgroup '/user.slice/user-1000.slice/user@1000.service/app.slice/app-stellarium-9969da1a5c0c472eaafd7801c4c84b28.scope': No such process
Jul 22 13:13:08 mycomputer systemd[1644]: app-stellarium-9969da1a5c0c472eaafd7801c4c84b28.scope: Failed to add PIDs to scope's control group: No such process
Jul 22 13:13:08 mycomputer systemd[1644]: app-stellarium-9969da1a5c0c472eaafd7801c4c84b28.scope: Failed with result 'resources'.
Jul 22 13:13:08 mycomputer systemd[1644]: Failed to start app-stellarium-9969da1a5c0c472eaafd7801c4c84b28.scope - stellarium.
Jul 22 13:13:08 mycomputer systemd[1]: Started systemd-coredump@2-263792-0.service - Process Core Dump (PID 263792/UID 0).
Jul 22 13:13:08 mycomputer systemd[1]: Started drkonqi-coredump-processor@2-263792-0.service - Pass systemd-coredump journal entries to relevant user for potential DrKonqi handling.
Jul 22 13:13:08 mycomputer systemd-coredump[263794]: [🡕] Process 263790 (Stellarium-25.1) of user 1000 dumped core.

                                                   Stack trace of thread 263790:
                                                   #0  0x0000000000409442 sqfs_block_dispose (Stellarium-25.1-qt5-x86_64.AppImage + 0x9442)
                                                   #1  0x000000000040c326 n/a (Stellarium-25.1-qt5-x86_64.AppImage + 0xc326)
                                                   #2  0x000000000040c1af sqfs_cache_destroy (Stellarium-25.1-qt5-x86_64.AppImage + 0xc1af)
                                                   #3  0x0000000000408f49 sqfs_destroy (Stellarium-25.1-qt5-x86_64.AppImage + 0x8f49)
                                                   #4  0x000000000040fc6e sqfs_ll_destroy (Stellarium-25.1-qt5-x86_64.AppImage + 0xfc6e)
                                                   #5  0x000000000040f4f6 fusefs_main (Stellarium-25.1-qt5-x86_64.AppImage + 0xf4f6)
                                                   #6  0x0000000000405df8 main (Stellarium-25.1-qt5-x86_64.AppImage + 0x5df8)
                                                   #7  0x00007f7071f1f24a n/a (libc.so.6 + 0x2724a)
                                                   #8  0x00007f7071f1f305 __libc_start_main (libc.so.6 + 0x27305)
                                                   #9  0x0000000000405ff1 _start (Stellarium-25.1-qt5-x86_64.AppImage + 0x5ff1)
                                                   ELF object binary architecture: AMD x86-64
Jul 22 13:13:08 mycomputer systemd[1]: systemd-coredump@2-263792-0.service: Deactivated successfully.
Jul 22 13:13:08 mycomputer drkonqi-coredump-processor[263795]: "/f2/sr/sa/Stellarium-25.1-qt5-x86_64.AppImage" 263790 "/var/lib/systemd/coredump/core.Stellarium-25\\x2e1.1000.cb9618cfc5f54fe2a4625c6fbe325a4c.263790.1753215188000000.zst"
Jul 22 13:13:08 mycomputer systemd[1]: drkonqi-coredump-processor@2-263792-0.service: Deactivated successfully.
Jul 22 13:13:08 mycomputer systemd[1644]: Started drkonqi-coredump-launcher@2-263795-0.service - Launch DrKonqi for a systemd-coredump crash (PID 263795/UID 0).
Jul 22 13:13:08 mycomputer drkonqi-coredump-launcher[263806]: Unable to find file for pid 263790 expected at "kcrash-metadata/263790.ini"
Jul 22 13:13:08 mycomputer drkonqi-coredump-launcher[263806]: QFile::remove: Empty or null file name
Jul 22 13:13:08 mycomputer drkonqi-coredump-launcher[263806]: Nothing handled the dump :O

For qjackctl, there is nothing strange in the journal, and the app appears in the systray but does not function properly (more information here: https://github.com/rncbc/qjackctl/issues/219 ). Journal output:

Jul 20 10:27:57 mycomputer kwin_wayland_wrapper[30965]: Omitting both --window and --windowclass arguments is not recommended
Jul 20 10:27:57 mycomputer systemd[1663]: Started app-qjackctl-5e41eada79da44df9382c144558b983f.scope - qjackctl.
Jul 20 10:27:57 mycomputer kded5[1799]: Registering ":1.229/StatusNotifierItem" to system tray

SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.27.5
KDE Frameworks Version: 5.103.0
Qt Version: 5.15.8
Using Wayland
Kernel 6.1.0-37-amd64 (64-bit)

Possibly related? https://bugs.kde.org/show_bug.cgi?id=469328