I made this app a week ago, it will check your stores marked as favourites on TooGoodToGo and check for available boxes on it. If there is one, it will send a notification to one of a few options (gotify, pushbullet, pushover or custom webhook). There are a few options for running it on interval, or one-time (which works well with cron).

I found it pretty useful as plenty of times I forget to check during times a box might be available, or I miss it completely.