On KDE Plasma, I would stick with Kate and hide/disable some the fancier interface features. It might seem like overkill, but since it’s built from common components that other KDE apps use using anyway, the additional resource consumption will probably be minimal. And it’s quick.
On a Gtk desktop, you might try Mousepad. This is what I used before moving away from Xfce.
On KDE Plasma, I would stick with Kate and hide/disable some the fancier interface features. It might seem like overkill, but since it’s built from common components that other KDE apps use using anyway, the additional resource consumption will probably be minimal. And it’s quick.
On a Gtk desktop, you might try Mousepad. This is what I used before moving away from Xfce.