I've been thinking of moving from GNU/Linux to BSD.
But I'm not sure whether a lenovo thinkpad 240
is a compatible laptop.
Has anybody installed ghostBSD on one?

Download "latest" version GhostBSD.org/download burn to USB flash drive. Boot USB flash drive live version ( copies from flash to ram, you may remove usb flash drive) and test live version on your PC system.

Other resources
Bsd-hardware.info. Or linux-hatdware.org
hw-probe -all -upload

Nomadbsd.org. Has the hw-probe utility. Burn nomad to USB flash drive and boot.

GhostBSD works on my Lenovo T430.

Download "latest" version GhostBSD.org/download burn to USB flash drive. Boot USB flash drive live version ( copies from flash to ram, you may remove usb flash drive) and test live version on your PC system.

Other resources
Bsd-hardware.info. Or linux-hardware.org
hw-probe -all -upload

https://bsd-hardware.info/?view=compute ... +%28All%29
Look at this info. I see openbsd tested on x240
The wifi device is listed

Nomadbsd.org. Has the hw-probe utility. Burn nomad to USB flash drive and boot.

GhostBSD works on my Lenovo T430.

What wifi device chipset is in your Lenovo 240?
Usbconfig list
Pciconf-lv

I'm running GhostBSD on a Lenovo X240 Thinkpad just now (writing this message).

Works great.
Even suspend works (little slow, I see console first, then it switches back to Mate Desktop).