That seems more a failure on LastPass's part than Firefox's.

I say this as a LastPass user, they clearly don't give a rat's ass. They've known about the WebExtension requirement for, what, a year now? Somehow they're among the first apps to support Android Oreo's autofill API, yet they can't be bothered to update their Firefox extension.

It's a real pity. I like LastPass. I pay for it. I use their Secure Notes feature ALOT. But I may still have to switch if they can't get their act together.