Might be a bit late of a reply, but I was able to install the Broadcom drivers super easy on my 2013 MBP. I know, different laptop, but same driver.
After installing Manjaro, KDE Neon, and Kubuntu, here’s what I did:
I paired it with my phone and shared my internet connection, then downloaded the Broadcom driver in the repo. Done!
I also installed Aurora (Fedora immutable distro) on it, and the Broadcom drivers were already installed, so it just worked, but every time my laptop went to sleep it crashed and I had to hold the power button to start it, so I gave up on that and installed Neon
Huh that’s strange because I’ve never had the driver break on me.
But I guess it means you’ve successfully installed the new card? Awesome