Single-word browser URL bar search terms logged as 'searchterm.lan' NXDOMAIN

The issue I am facing:
I have been using Pi-hole for years and may have only just noticed this...

On my network single word search terms entered into web browser URL bars are shown in my Pi-hole logs as 'searchterm.lan' NXDOMAIN.

I have observed this on search queries from Linux systems and Windows 10.

Screenshot below shows logs for 'ubuntu' entered as a search term into Firefox's URL bar on Ubuntu 20.04.2 LTS. iOS devices appear to behave differently.

I don't recall seeing this in the past with identical network equipment. Is this behaviour intended? If not what could be causing it?

Blocking and all Pi-hole features work without issue.

Details about my system:

  • Very latest versions of Pi-hole, Unbound and PiVPN running on the very latest Raspberry Pi OS.
  • Pi handles DHCP and this option has never been enabled on my Ubiquiti ER-X.
  • DNS is handled by Unbound as per official guide.
  • All three options under Advanced DNS settings are checked.

What I have changed since installing Pi-hole:
Nothing has changed.

Pi-hole isn't involved here - it just receives and processes those queries.
It is your clients that decide to issue those queries, so you'd have to look into your clients for the cause of this.

That said, it is not unusual for clients -even expectable- to append queries for a domain by the local search suffix (which seems to be lan in your case).

It would depend on a client's OS if, how and how well you would be able to control that behaviour (see e.g. Linux resolv.conf's man pages, specifically the search and ndots options).