As Android version is officially abandoned (see https://forums.lastpass.com/viewtopic.php?f=12&t=280445&start=80) - this extension became useless. Everybody uses mobile phones and everybody wants to use the same browser on desktop and on mobile to make use of sync, tab sharing etc.
LastPass app for Android without this extension doesn't fill in form fields in Firefox too.

Bye, LastPass! I switch to bitwarden, which works OK on Firefox for Android and offers more for less money.