How can I manage to allow only one application in MacOS Sonoma to access the internet

in a short while I will be reliant on a direct Iridium satellite connection only in order to get weather data. The grib files are the only data I will process on my Macbook. Now I know that usually once the Mac is connected to the internet all sorts of processes are sending and receiving data. I dont want that to happen as I am on a limited data budget with the mentioned connection. So I am wondering how I can most effectively prohibit the whole system to access the internet except that one process which will get the needed data. Shall I - Configure the firewall - Edit the hostsfile - Use third party software like Little Snitch Any pointers?