As an additional informaton, I've tried installing the vanilla LibreOffice 7.0.4.2 distribution from www.libreoffice.org, installed these three packages:
libobasis7.0-images_7.0.4.2-2_amd64.deb libreoffice7.0_7.0.4.2-2_amd64.deb libreoffice7.0-calc_7.0.4.2-2_amd64.deb libreoffice7.0-writer_7.0.4.2-2_amd64.deb and LibreOffice seems to work just fine 9even without xwayland installed)
