Setup for a DSI 4.3 inch display

I have a 4.3 inch waveshare DSI monitor which I have connected to a PI4 with the latest OSMC release but when I boot it I get the splash screen but then nothing. If I have an HDMI screen connected I get the OSMC home screen displayed as it should be.
Am I missing some setup to get the OSMC home screen on the 4.3 screen?
Thank you for your help

Quick search on DSI gives this

This should indeed do the trick – but it will incur a performance penalty.

Thank you guys for the swift response.

Will it slow the whole Pi down or just the rendering of the screen. I normally run this Pi as a TV recorder headless but I got given a screen so thought I would run it here for doing the upgrades