I have now upgraded/migrated the trades persons business listings directory to Drupal 9. I have used very few contributed modules and actually achieved most of the functionality with Drupal core. The only contributed modules I used was to add functionality that is not essential but do add more usability options like users being able to login using Facebook and the Address, geolocation and geocoder modules which make it easier for users to add their business to the map.
Check out the website here: https://www.my-local-trades.co.uk/directory/