The currently available preview builds, v632.0.73 and v632.0.72, get as far as displaying the menu bar before they hang for me on macOS 10.14.6. I can provide a sample or spindump on request. This is the first WebKit2 based build I’ve tried; the version I updated from was 630.0.318604. I’d check older builds and try to bisect but there doesn’t seem to be any way to find them.
Downloaded the latest built today, but it still hung. Then I loaded the old version from 2018, took a snapshot of the (empty) workspace on a hunch that it might be messed up workspace state causing the problem, and quit. After that, the new build launched OK.