I have tried all the colors of the theme, and it opens perfectly to me. [url]https://imgur.com/eunIIkd[/url] Is there a message that indicates the error?

No. When I open keepassxc from the command line: keepassxc mypasswords.kdbx Invalid Context= "Legacy" line for icon theme: "/usr/share/icons/Adwaita/8x8/legacy/" Invalid Context= "Legacy" line for icon theme: "/usr/share/icons/Adwaita/16x16/legacy/" Invalid Context= "UI" line for icon theme: "/usr/share/icons/Adwaita/16x16/ui/" Invalid Context= "Legacy" line for icon theme: "/usr/share/icons/Adwaita/22x22/legacy/" Invalid Context= "Legacy" line for icon theme: "/usr/share/icons/Adwaita/24x24/legacy/" Invalid Context= "UI" line for icon theme: "/usr/share/icons/Adwaita/24x24/ui/" Invalid Context= "Legacy" line for icon theme: "/usr/share/icons/Adwaita/32x32/legacy/" Invalid Context= "UI" line for icon theme: "/usr/share/icons/Adwaita/32x32/ui/" Invalid Context= "Legacy" line for icon theme: "/usr/share/icons/Adwaita/48x48/legacy/" Invalid Context= "UI" line for icon theme: "/usr/share/icons/Adwaita/48x48/ui/" Invalid Context= "Legacy" line for icon theme: "/usr/share/icons/Adwaita/256x256/legacy/" Invalid Context= "Legacy" line for icon theme: "/usr/share/icons/Adwaita/512x512/legacy/" Invalid Context= "Legacy" line for icon theme: "/usr/share/icons/Adwaita/scalable/legacy/" Invalid Context= "UI" line for icon theme: "/usr/share/icons/Adwaita/scalable/ui/"

I think it's a problem of the Adwaita icons. If you are using the Neon Knights icons, try opening the index.theme file in ~/.local/share/icons/ Neon-Knights-Blue-Folders and delete Adwaita from the inherit icons. If it doesn't work, install or reinstall the Adwaita icons. If it doesn't work, I don't know what the problem might be, but it wouldn't be about the theme.

Thanks

Thanks

Editing the .svg files and the color scheme