Can I get my stuff back?

Be warned, this question contains some major spoilers for the later chapters and the epilogue.

In the epilogue you continue playing as John Marston instead of Arthur Morgan. That means you also lose all the stuff you collected as Arthur and start with a very empty inventory. And while I got Arthur's weapons back at some point in the epilogue, I don't have much money right now at the start of the second part of the epilogue and almost no food for me or my horse.

Can I get any of Arthur's money, provisions and ingredients back during the epilogue? Or do I have to start hunting again to be able to feed myself and my horse?

I'd appreciate if any story spoilers are tagged as such for anything later than the point of the story I'm at.

I'll try and keep this answer spoiler free

When you start the epilogue you cannot get the money or consumables you lost back. All the cash you had in Arthur's inventory is permanently lost at the beginning of the epilogue. You do keep the clothes and the weapons you had purchased during the preceding chapters, but you have to get about a third of the way through the epilogue to access them.

The final mission of the epilogue will provide you with enough money that it should negate what was lost (for me personally, I gained about twice as much money as I had originally, and that was not a small number). You can continue playing after the final mission and use this new income to purchase the supplies that were previously lost.

One other thing, you keep all unique quest items, maps, and notes that you had from earlier in the game. Those are never removed from your character.

You can read all of this information, and answer other questions, from this USGamer RDR2 Epilogue FAQs page.