Until all of the PPAs get updated you are going to find a few instances where .debs designed for 18.04-18.10 are not going to install in 20.04. For instance, the snap version of Brackets is a steaming pile of crap and the latest .deb from December 2019 won’t install because it is looking for libcurl3 which isn’t available on 20.04. Easiest solution I have found, without resorting to messing with the libraries, is to simply fix the .deb which is pretty easy.
1. Download the .deb file from the Brackets Github repository
2. Move that file into a folder like /home/foo/Downloads/Brackets
3. Make a new directory names brackets-fix and extract the deb into that directory:
dpkg-deb -R /home/foo/Downloads/Brackets/Brackets.Release.22.214.171.124-bit.deb /home/foo/Downloads/Brackets/brackets-fix
4. Edit the control file and replace libcurl3 with libcurl4 which should already be installed on your system.
sed -i 's/libcurl3/libcurl4/g' /home/foo/Downloads/Brackets/brackets-fix/DEBIAN/control
5. Rebuild the .deb file and install it.
dpkg-deb -b /home/foo/Downloads/Brackets/brackets-fix brackets-fixed.126.96.36.199-bit.deb
dpkg -i /home/foo/Downloads/Brackets/brackets-fixed.188.8.131.52-bit.deb