Keyboard and trackpad not working on a 2015 MacBook Pro running macOS Catalina

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. 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. A friend of mine has sent me a USB flash drive with macOS Catalina on it to try a fresh installation. However, the problems are back and while trying to install macOS, 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.