Btw here is a write up for an arch linux installation (yay can be remplaced by any AUR helper)
- Install emacs
sudo pacman -S emacs

- Install ghcup and stack
yay -S ghcup-hs-bin
ghcup install stack

- Add $HOME/.ghcup/bin to your path by adding
export PATH=$HOME/.ghcup/bin:$PATH
to your bashrc and reloading your shell

- Use stack to install Agda
stack install Agda
this may take a while to compile
- ensure $HOME/.local/bin is in your path using echo $PATH, if not add
export PATH="$HOME/.local/bin:$PATH"
to your bashrc and re-log in into your session

- in ~/.emacs.d/init.el (create the directory .emacs.d if it doesn't exist) add
(load-file (let ((coding-system-for-read 'utf-8))
             (shell-command-to-string "agda-mode locate")))
(add-to-list 'auto-mode-alist '("\\.lagda\\.md'" . agda2-mode))

- Start emacs and edit some Agda files