It's a pretty simple process...
1. Open the CC Desktop App
2. Click the Apps tab
3. Click the small triangle next to DW's Open/Update button
4. Choose Manage > Other Versions
5. Install the previous version you like
All of the versions listed there can be installed on the same machines at the same time. They won't run concurrently, but it allows you to keep using a version you're familiar with (that works correctly) while troubleshooting continues on the "latest and greatest".
In the future, make sure the checkbox for "Remove Older Version" is disabled in the installation dialogue, under Advanced Options, until you're sure the newer version will work for you.
(I still have CC2015 along side 2019)