One of the most frustrating things about traveling is that flying is almost always the cheapest option if you want to travel more than a few hundred km. It's absurd that putting a massive, fossil fuel-guzzling machine 12km up in the air is somehow cheaper than taking a far more environmentally friendly diesel bus or electric train. I'm convinced this is a result of some kind of bullshit subsidy or tax break for airlines. The fact they managed to scam even more money out of the government during COVID while bus companies literally went under is obnoxious to me.
Anyway... Rome2Rio is a great site, and it does provide lots of useful info on bus travel. But what it doesn't always do is find the best/cheapest fare. Some companies have special deals if you book far enough in advance, or on specific days, so unless you are doing last minute travel you might be able to work something out.
Another trick you can use is to look at so-called Chinatown buses, or casino buses (depending on where you are going). Chinatown buses can be quite cheap, but you need to have the inside scoop to find out where they leave from and where they are going. Casino buses can sometimes be free - they will take you from an urban center to a casino, with the assumption you are going to the casino to spend money, so you get some credit on the machines, which you might be able to immediately cash out to get your money back. If you can find one that goes back to a different city, you might be in luck.
The other thing worth checking out is local public transport - sometimes in large metro areas on the east coast you can travel 100km or more on a local ticket.
Of course all this will require doing a bunch of research, or just heading out boldly and figuring it out when you get there, but if you enjoy the process of travel as much as getting to the destination... might be fun. Flights will always be faster and safer, though, and almost always cheaper, if all you care about is getting to the place.