Tmux

El famoso terminal multiplexer (sorry not sorry but screen is a piece of shit).

Sync panels

Sync panels can be quite usefull to do the same tasks on a different set of servers.

tmux.conf file

[...]
unbind S
bind S set-windows-option synchronize-panes
[...]

How to use it

Typical use case can be updating let's say 3 Debian servers.

1. start tmux
2. split in 3, use ssh to connect to the targets¹.
3. use bind prefix + S to activate sync²
4. apt update && apt upgrade
5. And voilà !