Depending on your project, you might want to consider using EditorConfig (https://editorconfig.org/). There's a Notepad++ plugin which will load an .editorconfig where you can specify "lf" as the mandatory line ending.
I've only started using it, but it's nice so far, and open source projects I've worked on have included .editorconfig files for years. The "EOL Conversion" setting isn't changed, so it can be a bit confusing, but if you "View > Show Symbol > Show End of Line", you can see that it's adding LF instead of CRLF, even when "EOL Conversion" and the lower bottom corner shows something else (e.g. Windows (CR LF)).