I’ve already suggested what I’d probably do.
As I’ve stated elsewhere I had a dell laptop which had issues with its internal display when it got warm, so I experimented with alternatives & was happy with it until it’s hdd also died then decided it wasn’t worth the hassle. Yes you can ‘mirror’ displays, but I don’t think it’s reasonable for developers to make allowances for someone wanting to install on a device with a non-working display, especially given there are workarounds like I suggested.
I’ve also heard on a podcast another Ubuntu flavor’s developer discuss dead laptops, failing hardware, and expecting *Ubuntu to cope with it, he felt they should just buy a cheap raspberry pi & use that instead. I wasn’t a fan of the suggestion, but in the long run it does make sense as newer hardware will cost far less to run (the initial outlay versus power savings)…
I’ve not installed Lubuntu using LXQt and a dead screen, but I did so with Lubuntu using LXDE, opting for the install I mentioned in the other post (or I started with the Ubuntu Server ISO; I can’t recall).