20.04 needn't take up much space. The 20.04 installation on one PC I currently have up ATM is on an 8G / filesystem, with separate FHS filesystem only for /home. 73% is in use. It's probably never had a kernel removed, so there are currently 9 installed. Cut the number down to 2 and filesystem in use would almost certainly be below 50%.
If you want a modest installation, do a standard install without recommends, by appending the following to the installer's kernel command line:
Code:
tasks=standard base-installer/install-recommends=false
This should produce an installation in the neighborhood of less than 25% of 8GB total space in use on an EXT4 / filesystem. After installation is complete, create
/etc/apt/apt.conf.d/00InstallRecommends containing
APT::Install-Recommends "false"; install the DE and DM and additional software of choice, and you should have a very respectable amount of space free for personal data and some apps you didn't already think to add.