Multisite main site as a wayfinder/sub-sites selector

Hi, I’d like to have the main site of the network as a landing page offering the choice of all the sub-sites available. Ideally this would be a simple page with only the logos and slogans (below logos) pointing to the sub-sites. This would be displayed in a (responsive) grid. Nothing else on the page.

I’m wondering what would be my best options out there? Any widget would offer this? Any theme/child theme?
Google did not really help me with a relatively easy solution yet but I’m thinking I’m probably not the first one to want to build such a simple thing, am I?!

Cheers