Some applications on Ubuntu 19.10 very slow to start

After having the same problem and doing strace + a lot of reasearch I found out that this fixes the issue for good (filezilla, keepassX etc. all launch instantly now):

sudo apt-get install appmenu-gtk2-module

Then reboot.

Cannot confirm that installing appmenu-gtk2-module solves the problem. Also the "dbus-launch --exit-with-session" only provides a partial solution. For example VLC is facing the same startup issues. Starting it as "dbus-launch --exit-with-session vlc" avoids the described startup delay. However, integration into top panel and raven is lost in Budgie desktop.

Hence the question what exactly causes this problem and how to really solve it is still open.

Edit: I would like to clarify, what I consider being not OK with VLC when executed with dbus-launch. I attached four screenshots - two being suffixed with OK which show the integration into Budgie when being executed without dbus-launch. The second set - suffixed with NOK shows it being executed with dbus-launch. The difference is particularly noticeable in the vlcRaven screenshots. Furthermore the behavior when clicking the top panel icon is different. With dbus-launch left-clicking the icon reveals the shown menu, while the same hides/shows the application. The menu is opened upon right-clicking the icon. I do not consider the different behavior as showstopper for me though it might provide additional hints what's actually causing the issue.

VLC Raven panel NOK VLC Raven panel OK Top panel NOK Top panel OK