/s heavy tmux user that left it for xmonad.
The only terminal emulator that supports selection with keyboard afaik is rxvt with plugins. I would be interested to know if there are other terminals that support this. Please don't say emacs XD
Run rxvt if you like.
I use a multiplexer because it lets me instantly open a new terminal in the same directory I'm currently working in. Furthermore it can open the terminal's buffer in Vim, letting me select and copy text using all features and shortcuts I'm used to. Doing the same by scrolling around, selecting snippets using the mouse and pressing Ctrl-Shift-C cannot compete with that.
Yes, there are a few terminal emulators with integrated tabs and window splitting and all that which offer similar features, but then they also have countless other things I don't need and in return take ten times longer to open a new window.
You can add a keybinding for this with alacritty:
{ key: N, mods: Command, action: SpawnNewInstance }
alacritty has vi mode which gives you all of those keybindings without having to open vim (ctrl+shift+space).
It doesn't give me access to my custom keybindings or the plugins I have setup in Vim. Also I can't select or annotate terminal output and then save it directly into a file in one step.
The multiplexer is both more powerful and flexible by actually doing less and just passing tasks like selection and copying to other proven tools. I appreciate that more than terminals trying to do everything.