Guys, can you please tell me if there are actually any browsers that already have a proxy built in? I would like to find at least one of them. I'm tired of constantly downloading a separate proxy and installing it in my computer.

Yes, of course, such browsers exist and are quite popular among different users, both simple and those who are engaged in some commercial and any other activities on the Internet. You can familiarize yourself with a selection of the best proxy browsers here https://cross-browser.org/collections/best-proxy-browsers/ .