I used
set -g mouse on
bind -n WheelUpPane if-shell -F -t = "#{mouse_any_flag}" "send-keys -M" "if -Ft= '#{pane_in_mode}' 'send-keys -M' 'copy-mode -e; send-keys -M'"
from https://superuser.com/a/1007721/325613 to allow my mouse to scroll tmux.
However, I want clicking and dragging to use my terminal's default selection, not tmux copy mode's.
I am on macOS Terminal.app ssh'd into a bash shell running on Ubuntu. It is tmux 3.0a.