Recently (ver 7.4) the startup speed of LibreOffice Calc went from 20 seconds to ~ 60seconds, even with an empty sheet. Other programs like Gnumeric start up in 2 seconds. I already tried clearing the recent file history, starting in safe mode, renaming ~/.config/libreoffice/4 , disconnecting network, tried ver 7.5 without improvement. Starting Writer is also just as slow. I am using Arch Linux, and pulled the standard packages from the repository.
Solved the problem from the ArcoLinux Discord server comments today, remove: xdg-desktop-portal-gtk xdg-desktop-portal-gnome
There has been no code patch that has fixed the problem, so fixed is not the right thing to close the bug. In this case, not our bug, or it works for me.