Session restore doesn't remember whole session so applications like Caprine are not restored. Caprine on my system is installed from .deb to reproduce: 1. Install Caprine, run it 2. Log Out from session or Restart PC 3. Caprine not brought back expectations: Caprine is restored with remaining applications This is KDE neon 5.17, but bug was occurring in 5.16, and probably 5.15 as well.
Applications need to follow the standard session protocol in order to get restored correctly. https://www.x.org/releases/X11R7.7/doc/libSM/xsmp.html Please also report to caprine. If they claim they have session restore then reopen this and we'll investigate what might be going wrong between us.