As the unfortunate owner of a same-gen MBP with the same wireless card, you're looking at using the proprietary driver (I at least never had any luck with the open-source ones). Luckily, Debian do support those, and even have wiki page for them: https://wiki.debian.org/wl
Does require some extra configuration though. If you happen to have a Android phone, you should be able to use that for USB-tethering to have internet access on the device you're installing on, will make the process a lot easier (you don't even need a SIM in it, you can tether your wifi, that's what I ended up doing ๐ ).
Quick tip for the author and those reading, instead of doing as in the article noted e.g.
sudo nanoor the like, you can usesudoedit(orsudo -e). The advantage of this is that it will use whatever you have configured as an editor (through$SUDO_EDITOR,$VISUALor$EDITOR), and will use your configuration files while editing instead of root's, meaning if you have a sick custom neovim or emacs setup you don't have to keep those settings files in sync with the root account. ;)