Getting Apple TV to access a shared library

Hi there,

I searched this forum and couldn’t readily find what I wanted - so apologies if it’s out there already and I missed it.

I have the the latest edition Apple TV and an older iMac (mid 2011) where I store a load of video files like home movies. I’ve previously been able to use Home Sharing to watch these files via the Computer app on the TV. The Mac has just become too old to update with the latest version of macOS (Mojave) and iTunes. I can longer access my iTunes library (the one stored on the Mac) from the Apple TV. I can see everything in the cloud/from the store, but not from the Mac. Help files suggest I need the latest version of iTunes, but it seems I can no longer download this.

Any my ideas on how to access these files on my TV?

Thanks.