I highly recommend Michelin XPS Ribs in this size. These are labeled LT, but they are actually Michelin commercial truck tires rated for “all position” use - drive, steer, or trailer - which means they are just as appropriate for trailer use as any ST tire, but the construction is light years better. For one thing, ST tires simply don’t undergo the same degree of testing as tires that are to be used on passenger vehicles. But the XPS Ribs in particular are especially tough - they are steel belted in the sidewalls as well as the tread.
I started using them after a lot of research after a blowout on I-81 of a (well-maintained, properly inflated) ST tire on my 3H GN (while carrying 2 horses). They are quite expensive, it’s true, but I’ve found the (relative) peace of mind a worthwhile expense. Google and you’ll find them exceedingly popular and highly thought of among towers of RVs as well as horse trailers, and you’ll find lots of info about them, especially as they’ve been around a while (there’s less about the Goodyear Endurance, which are very new still). I’ve found RV forums to be good sources of information and opinion about this sort of thing.
I however don’t fully agree with the “ask the tire guys” advice. You might find a good one, but in my experience, lots of “tire guys” have no idea what they’re talking about when it comes to trailers. Neither do lots of “trailer guys” for that matter!