Given Lubuntu 21.04 is now in it’s last week of support, I’d release-upgrade asap or if it’s a new install (you mention installing but gave no timeline though your wording implies to me it’s a recent install) I’d re-install a release that has will still be supported next Friday (21 January 2022).
I’m also unclear to me what you’re comparing it to, was it an older Lubuntu? (in which case what release, when was the upgrade; how achieved as I wonder if there are clues there?) or another OS. Also is the on-screen keyboard you’re asking about at sddm or the greeter/DM or something else?
You do mention BIOS password; but that’s under firmware control and thus before the OS has started; thus Lubuntu plays no part; sorry I’m confused by what you’re asking.