Worked for me. Installed it from a modified deb, apt keeps wanting to update it from the one in the ppa but it won't as long as the conflict is still there.
Yes, libraw20 breaks libraw19 because the deb control has libraw19 set conflicts and replaces. Replaces shouldn't be set because it doesn't overwrite anything. I'm not sure if there is actually a conflict but there doesn't seem to be.
You can get it to install if you download the deb:
apt-get download libraw20
ar x libraw20_0.20.0~202008211452~ubuntu20.04.1_amd64.deb
tar -xf control.tar.xz
delete Conflicts: libraw19
delete Replaces: libraw19
tar --ignore-failed-read -cvzf control.tar.gz md5sums control
Repack the deb
ar rcs libraw20_fixed.deb debian-binary control.tar.gz data.tar.xz
sudo dpkg -i libraw20_fixed.deb