Termux

@scottbilas reported that termux uses a custom clip tool.

You can configure it with:

set -g @extrakto_clip_tool termux-clipboard-set

If you share your tmux config with multiple OS's, this might work better for you:

if 'command -v termux-clipboard-set' {
    set -g @extrakto_clip_tool termux-clipboard-set
}