For me it was org mode (with evil mode because I was coming from 15+ years of Vim). Then..
"Oh, I can manage files and edit a directory like a file buffer.."
"Oh, I can SSH into systems and edit files but it doesn't even feel like SSH.."
"Oh, this makes a great, distraction free IDE.."
I recommend a batteries included distro like Doom Emacs or Space Emacs.