Most folks have plugged in a home router and setup WiFi on their own home network. You pull out your phone and find your network listed, type in your router password and you're good to go. Not many folks have ever thought about setting up their own LTE & 5G Network, but those with the talent like Maciej Mazur have done just that. Check out his post on Ubuntu.com
With about $300, a Raspberry Pi and a few other things, you can get started. Want to play with more advanced Mobile tools? Well, price might jump up rather quickly to $10,000 or more. Some hobbies can be more expensive than others! 😳