I'm having the same problem while setting up MFA in LastPass. To clarify the step details:
On the page "Set up mobile" on my PC browser the QR code is shown.
I the LastPass Authenticator app (on Android) I tap "Add Account".
Scan QR Code comes up. The device scans for quite long then gives the error "Unrecognised QR Code".
Could you try uninstalling the LastPass Authenticator app, restarting your device then reinstalling the app and seeing if you can then scan the QR code from your PC to finish the set up?
I am also having this problem on Android 11, Unihertz Pocket Titan.
Reinstalling the app does not help.
The app opens the camera and asks me to point it at a QR code. The app does not recognize or scan the QR code I am presenting.
Other apps on the phone scan QR codes just fine (including the one provided by Lastpass, which appears to be an otpauth:// link.
Is there a way to copy the link into the Authenticator app directly?
I had the same problem with Whatsapp on the web but NOT with Android Messages web site.
I realized it was some glaring, reflections, lights interfering.
So I used my hands to make some sort of tunnel between the phone and the screen.