As per the release notes, Ubuntu 20.04 is not supported.
Link to the release notes for your reference: https://software.intel.com/content/www/us/en/develop/articles/intel-oneapi-dpcpp-system-requirements...
Regarding when Ubuntu 20.04 will be supported, we need to check with the concerned team and we will let you know at the earliest.
Sorry for the inconvenience, we will support 20.04 within this year but not decide which release yet. Please check the release notes for the new release as Rahul point out and let me know if you have further questions.