Need Browser for OS Mountain Lion 10.8.5

I sure wish it were that easy. I’ve been working on this for over a week! I’ve googled everything. The only OS that will load on it is Mountain Lion 10.8.5 and I have to update in the proper order. My understanding after hours of research is that I need ElCapitan first than on to Catalina. I’m heading a brickwall. I cannot find a way to download any older systems. It definitely won’t download from the laptop I’m working on as the browsers won’t work with the OS and I can’t get to a download for anything that will work. It’s been an awful cycle. The laptop worked absolutely fine before I wiped it to sell it. Even had it all setup when we discovered the Safari browser would not work on the OS. I’m really mad that Apple puts these brick walls in place.