Thanks for telling us what you found. Great pics! I hope that is the only cause of the seizing.
Nasty hub and brakes, for sure, but they'll clean up. I had some that looked almost that bad. I started with lots of water to get the dried mud and gunk out. Just turn the hose on it. Then, remove the brake shoes and the brake cam. That cam must be cleaned up or your brakes will never work properly.
Now, follow the manual about inspecting, lubricating and replacing parts. Here's a link to the parts schematic to help you. https://www.partzilla.com/catalog/ho...ar-brake-panel
You can see that there are bearings, seals, etc that will need to be replaced. Don't skip this step or you'll be right back where you started the next time it seizes up, and it will.
I use Simple Green as a general cleaner. You can also used Brake Clean in spray can and it cleans things up nicely but you need to get most of the gunk off first or you waste a lot of product. I always have a can of PB Blaster handy as well as purple grease.
You can use some fine sandpaper, 220 grit, and clean up the inside of the drum as well as the brake cam. Some members use a Dremel with sanding drums.
Again, follow along with the manual and you'll be happy with the result! We'll be here to help you if you need it.
Forgot to add the disclaimer. LOL. Brake dust can contain asbestos. You should wear a mask while cleaning the brakes. Clean at your own risk.
I don't look good in a orange jumpsuit.