In KDE5 session on Wayland the gnome is selected: https://github.com/LibreOffice/core/blob/293526165fcd236ba1742de2feec6ea06376e83f/vcl/unx/generic/desktopdetect/desktopdetector.cxx#L283 This should be adopted to load up based on which session is really running.
Confirmed with Version: 6.3.0.0.alpha0+ Build ID: cb04f8bf4f46c573edcf7be5c33d5f06d89eaff4 CPU threads: 4; OS: Linux 4.19; UI render: default; VCL: gtk3; Locale: en-GB (en_GB.UTF-8); UI-Language: en-US Calc: threaded @Tomáš: Since you've already found the corresponding place in the source code: Are you planning to work on this yourself? Otherwise, I'll probably take a look as I find time.
Honestly soonest I could get to this is next week to do it properly. So please shoot ahead :)
https://gerrit.libreoffice.org/#/c/67044/
Michael Weghorn committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/core/+/7eccf0b3fe771a519dbdaaf536d64b5b193a723f%5E%21 tdf#123011 Detect kde5 desktop in Plasma Wayland session It will be available in 6.3.0. The patch should be included in the daily builds available at https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: https://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
Michael Weghorn committed a patch related to this issue. It has been pushed to "libreoffice-6-2": https://git.libreoffice.org/core/+/3e4478103ee1ba912d650ab447ed246f5f1cc196%5E%21 tdf#123011 Detect kde5 desktop in Plasma Wayland session It will be available in 6.2.1. The patch should be included in the daily builds available at https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: https://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
Michael Weghorn committed a patch related to this issue. It has been pushed to "libreoffice-6-2": https://git.libreoffice.org/core/+/1124e98e935cec42c51f25f1fc713285b1044d07%5E%21 Revert "tdf#123011 Detect kde5 desktop in Plasma Wayland session" It will be available in 6.2.5. The patch should be included in the daily builds available at https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: https://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.