About window from FreeFileSync is placed behind the main windows on first launch. This gives the impression that the program crashed.
LXAppearance doesn't change the GTK themes because of GTK_THEME environment variable. The problem is that we need to set this variable because of GTK4 and Libadwaita applications.
KNOWN ISSUES
GTK_THEMEenvironment variable. The problem is that we need to set this variable because of GTK4 and Libadwaita applications.