I wanted to specifically install
libpython3.7-dev but it wasn't available in my default apt repositories.
My apt repositories had
libpython3.8-dev which wouldn't work for my specific use-case.
I am on PopOS 20.04. So the corresponding debian codename would be "buster".
I noticed that it was available in https://debian.pkgs.org/10/debian-main-amd64/libpython3.7-dev_3.7.3-2+deb10u1_amd64.deb.html. But it's really hard to keep resolving dependencies.
I needed apt to fix it for me.