I have a Macbook Pro (early) 2015 and roughly 2 years ago, the Keyboard and the Trackpad stopped working. So I stopped using it.

Two days ago, I had the idea to try it again. And it did still not work (how unfortunate!).

Then, I tried to install Pop!_OS via USB and I was able to use my Keyboard and my Trackpad already during the installation process.

I friend of mine has sent me a USB stick with OSX Catalina on it to try a fresh installation. However, the problems are back and while trying to install OSX, I am again, unable to use my Keyboard nor the trackpad.

What could be the problem here? The hardware itself works fine for obvious reasons.