I am on Ubuntu 18.04 x64 and LibreOffice 126.96.36.199. I want to remove the distro LO and install the 6.4 .deb from LO. Will I lose any work done with Base where I have DBs, queries, and Forms?
Have not had any problems previously removing distro, ppa, or tdf versions and replacing with something else.
If you have any concerns, create a backup of you system (or files). Best to do this on a regular basis anyway.
You can (as has been recommended) use a PPA version. See → “LibreOffice Packaging” team