If you copy the release version of 20.04 and use zsync, it is 86% the same.
Code:
fred@Z170N-focal:~/ISO$ zsync http://cdimage.ubuntu.com/ubuntu/daily-live/pending/groovy-desktop-amd64.iso.zsync
****
Read groovy-desktop-amd64.iso. Target 86.6% complete.
downloading from http://cdimage.ubuntu.com/ubuntu/daily-live/pending/groovy-desktop-amd64.iso:
#################### 100.0% 7474.7 kBps DONE
verifying download...checksum matches OK
used 2354110464 local, fetched 364393684
