Playing 4K Video on 1080p TV

My dad currently has a 1080p TV and a Raspberry Pi 2 running LE 9-10 (ish) but that has died, so it's time for a replacement.

I want to set up a Raspberry Pi 4 for him, so he can use it now and also take advantage of 4K output when he upgrades his TV to 4K for Xmas.

If I set up a RPi4 and latest LE/Kodi with Settings > System > Display : Resolution set to 1080p, what will happen when he plays a 4K video file? If I whitelist modes up to 1080p only, will it downscale 4k content?

I suppose I could try this on my TV, but it is 4K and I don't know how to confirm it's actually outputting 1080p while playing...

Cheers

Great!

For that to work properly do I need to whitelist the modes the tv supports?

I know Kodi doesn’t support tone mapping yet, so will definitely not give him any HDR10 videos until he upgrades his tv. Might run them through a Handbrake color filter if I need to.

Nice thanks