Currently the safari extension does not work on Catalina when it comes out. This is as I believe safari extensions must be associated with a Mac app now. They blocked support for extensions outside the store in Safari 12, but I believe they are now blocking all extensions, even ones in the store, that do not come with a Mac app. Lastpass updated theirs so the extension comes with the app recently. https://blog.lastpass.com/2019/01/change-safari-extension.html/
I was Googling importing PW into BW from keychain and came across a reddit thread where the BW developer says he isn’t likely to have a Safari extension. As someone who just moved their team to BW from 1P this is pretty close to a deal-breaker. Major bummer to read this.
I am not sure we will be able to continue supporting Safari in the near future.