Problem with executable file in Manjaro Arm on Pi

Hi all. I am following this guide to create a dedicated working keyboard from the Pi 400.

Anyway, this part went ok.
chmod +x pi400kb
But this line errors out - no such file or directory.
sudo ./pi400kb
Any ideas how to execute this file?
Do I need those quotations in this case?

Why not just build this app from AUR:

pamac build pi400kb-git

and start & enable service:

systemctl enable --now pi400kb.service

Many thanks Tomek.
Initially I came across this error.

ERROR: Cannot find the fakeroot binary

Google came to my rescue - I needed this to complete the build.

sudo pacman -S --needed base-devel

On to my next step. . .