I have the a few phones all of which have been suffering with biometric issue for many months but after reading the post from another contributor I have been able to get all phones working again after the March security update was installed
1. Open Lastpass on Android
2. Open the menu icon top left
3. Press the gear icon bottom left
4. Press Actions
5. Press Clear LastPass Cache
6. Press Refresh Vault
This has resolved the issue on Pixel 4a, Xiaomi Mi A2 and Xiaomi Mi A3
I hope this helps someone else
Same issue here on OnePlus 7 Pro with Microsoft Edge browser. My phone has an on screen fingerprint reader.
There is some improvement for apps, browsers and web site code that provide direct access to the new Android autofill service, but for anything that relies on legacy accessibility its still broken. The app doesn't gracefully allow to have both the autofill and accessibility hack turned on, they stomp all over each other, popping up when I dont need both, not popping anything up when I want one, and not working with fingerprint part of that time. Other password mgrs have committed to putting it in the keyboard and it is slick. Lastpass is a dinosaur. Its annoying to say the least.
Does the LastPass app support the new Android 11 Autofill API? I recall they do not and they still haven't as of early this year.
My guess is "no". According to the document you posted, "input method editors" like LastPass should be able to display autofill suggestions in-line, rather than in a drop-down. I have Android 11 on my Pixel 3a XL phone, and the LastPass app version 184.108.40.20670 (updated 4/12/2021), and it does the auto fills with drop downs.
It does successfully authenticate with my fingerprint, in both Chrome and in other apps, without crashing those apps. So I'm pretty satisfied now.