Setting up graphics drivers on an old laptop

so this is more of a reminder to myself in case I end up doing this again, but I was recently given a laptop by a friend and I decided to format it so it could run Debian

The install went well and everything ran fine, but the graphics drivers were wonky, for some reason. The panel's native resolution is 1366 x 768, but the install kept defaulting to 1024 x 768 with no other available options. I tried reinstalling some available drivers, the open source ones, even wiping the drive and trying to install an old version of Mint, but nothing worked. I probably spent a good 3-4 hours on it, until I finally found the post that saved me. I'll link it here for posterity and in case anyone else is going through the same issue.

The issue I was having made itself known during booting and had to do with 'radeon kernel modesetting' - in a nutshell, the graphics drivers weren't installed because they're non-free, which is kind of lame but whatever.

solution: edit your /etc/opt/sources.list file to append non-free contrib to the end of your primary repository.

it should look something like this: deb https://ftp.us.debian.org/debian/ testing main non-free contrib

                                                deb-src https://ftp.us.debian.org/debian/ testing main non-free contrib

The text that needs to be appended is in bold.

Hope this helps someone!