demm KaOS is not Debian based or using apt. To add packages not in the repo, see how to build those yourself: https://kaosx.us/docs/package/
cristianfb demm This apply in other programs like:? https://www.nylas.com/nylas-mail/ https://line.me/es/ https://brave.com/
demm KaOS has limited repos, so yes, whatever you miss and is not in KCP, you will need to build and maintain that way.