I'm interested in this as well.
I was going to repurpose my iPhone 5 with iOS 10.3.4 for Home Sharing iTunes Music, but I can't seem to share from my iMac with Big Sur. No Home Sharing option shows up in the iPhone Music app menu. [Edit: That's wrong. See below after the EDIT.]
However, it works fine on my iPhone SE (original) with iOS 14.4.
BTW, the iPhone 5 is very slow. It seriously lags, even with just basic OS navigation. Its A6 with 1 GB RAM just isn't up to the task. The iPhone SE with A9 and 2 GB RAM feels much, much faster.
EDIT:
Home Sharing problem solved with the iPhone 5. I made a n00b error - I was on the wrong WiFi network. Once I hopped onto the right WiFi network, it connected fine. However, it was very, very slow to load, painfully slow. What makes it worse is that every time you leave Home Sharing and go back into it, it has to reload. And it takes forever each time. So I still would not recommend it on something as old as the iPhone 5.
It takes almost 10 seconds to load my Home Sharing Music library database on my iPhone 12 Pro Max, and longer on the iPhone SE. It's just horrible on the iPhone 5, like a minute or something. Hope that helps.