Xterm does this via DEC protocol commands. Well, it does this by specifying double-height, double width, or both. Why does Kitty have to do things its own way yet again?
Thanks, I was also wondering! I wonder what it would take (politically) to get Konsole to support this (kind of afraid to just file the bug and find out!)
VTE based terminals can't support this AFAIK. Kitty draws itself with OpenGL and so supports these things. Iterm2 is also a similar story afaik (and Wezterm and ....)