Locale switch does not work on Rails 7 using a form

I'm aware this has probably been asked before but for some reason I can't get it to work with button_tags. If I modify the URL manually it works perfectly.

routes.rb

Rails.application.routes.draw do
  # For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
  scope '(:locale)' do
    root 'welcome#index'
    post 'set_locale', controller: 'application'
    get 'who_we_are/index', to: 'who_we_are#index', as: 'who-we-are'
    resources :properties
  end
end

application_controller.rb

class ApplicationController < ActionController::Base
  before_action :set_locale

  def set_locale
    I18n.locale = params[:locale] || I18n.default_locale
  end
end

application.html.erb

<ul class="navbar-nav ms-auto">
  <li class="nav-item">
   <%= form_tag('/set_locale') do -%>
       <%= button_tag '&#127482;&#127480;'.html_safe, name: 'locale', value: 'en', type: 'submit', class: 'btn' %>
       <%= button_tag '&#127466;&#127480;'.html_safe, name: 'locale', value: 'es', type: 'submit', class: 'btn' %>
   <% end %>
  </li>
</ul>

When clicking on any of the buttons (code is an emoji flag FYI), nothing happens. This is on the log:

Started POST "/set_locale" for ::1 at 2022-09-21 00:19:25 -0600
Processing by ApplicationController#set_locale as TURBO_STREAM
  Parameters: {"authenticity_token"=>"[FILTERED]", "locale"=>"en"}
No template found for ApplicationController#set_locale, rendering head :no_content
Completed 204 No Content in 3ms (ActiveRecord: 0.0ms | Allocations: 504)

The no_content warning leaded me to think that I had to add this after the I18n.locale = params[:locale] || I18n.default_locale line:

respond_to do |format|
 format.html { redirect_back(locale: params[:locale], fallback_location: root_path) }
end

Doing that sends the page into infinite redirects. Ideally, I'd want that the buttons redirect to the same page but with different locale (my URL format is localhost:3000/:locale/the_page), but if it's not possible, I'll be happy with root_path.