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: 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 😅).