... This will affect a lot of people, and we understand it will be disruptive for many as we all get used to the new way of doing things. Our documentation about this aspect of using Python on Raspberry Pi is at rptl.io/venv; if you try to use pip the old way, you'll see an error message which includes that link. There, we set out exactly what you now need to do in order to install packages via pip.
https://www.raspberrypi.com/documentation/computers/os.html#python-on-raspberry-pi