Browsers are literally the best attempt at the everything app.
There’s already been a lot of good answers on this. But a goody oldie article on making a browser is covered in Matt Brubeck’s 2014 article, Let’s Build A Browser Engine.
If you want to see one of the most minimal source code for a terminal based browser that is still in use today, I recommend downloading the source code for the Links Browser. Note that this site is very old and doesn’t even use https. But the source code can still be had here.
Browser software is super interesting, but there’s a lot even for a bare minimum setup like Links, so that’s more or less why most people don’t develop new ones from scratch anymore. Though there are a few exceptions like Servo, and Surf but they are pretty buggy tbh. Hope that helps and sparks your interest.
EDIT: Also of interest is Tali Garsiel’s article, How Browsers Work. This is probably one of the best in depth articles on the subject.
Damn…this looks really good actually. I’m sad to day I never heard of cohost until now. But I’ll admit I just identify with the founder’s sentiments around the tech industry, and their strict adherence to moral values around how a platform like that should interact with their users. I wish their developers all the best in looking for new work.