Send Ctrl+<n> through to Neovim in foot terminal with tmux

Hi, looking for some help. I really want to be able to use bindings like C-1, C-2, ... in Neovim. However, I am aware that with many terminals C-1 sends 1, C-2 sends C-@, and so on.

With just Neovim and foot terminal, it works with no additional configuration - hitting C-1 activates my C-1 binding in Neovim. However, when running tmux, it doesn't work.

I believe the solution will lie in some combination of the following lines in my config

set -ga terminal-features 'foot*:extkeys'
set -g extended-keys-format csi-u
set -g extended-keys always
set -g xterm-keys on
set -g allow-passthrough on

The only thing that makes a clear difference is extended-keys always which for some reason makes C-1 work as desired but no change in behaviour for C-2, C-3, C-4 (still sending C-@ etc... however, C-1 now sends ^[[49;5u ... I will not pretend to know what this means, I am not a terminal expert)

I'll be honest and say these are just lines I've picked up from stackoverflow posts and github issues that seem related. I have also seen there is something called the kitty key protocol that might lead to a solution.

Any help is welcome. I love working in the terminal but god damn the layers of tech debt, abstraction, protocols and so on make this seemingly simple thing so complicated.

Tmux 3.5, by the way.