Says Image file corrupted.
Tried twice. No luck. Tried running Disk FirstAid and the issue persists
Where did you download your dmg file from (it worked on my Catalina system)? May be you preferred download mirror has a corrupted image and you may want to change it using manually pick a mirror, which is a link on the download page appearing, when you have started the download (or use link: https://download.documentfoundation.org/libreoffice/stable/7.0.0/mac/x86_64/LibreOffice_7.0.0_MacOS_x86-64.dmg.mirrorlist and pick your mirror manually there. This page also provides the exact sizes of the download by bytes and proper checksums, which can be used to verify your download)
Solved:
DOwnloaded it again using Safari browser & it worked fine. Had issues downloading from Chrome
(repeating Milindsoman comment as answer):
Solved: DOwnloaded it again using Safari browser & it worked fine. Had issues downloading from Chrome