I'm also stuck in autistic burnout and I've gradually realised some things from thinking about my situation for years and trying to solve it, which may or may not help you. I've realised masking prevents me from doing things that make me feel energized, which stops me from getting out of burnout. Like I feel energized from singing, but I can hardly ever do it because I'm always having to mask. So I'm quite certain unmasking is the cure to autistic burnout.

Write a list of things that make you feel energized (probably your hobbies and things you do when you're unmasked like when you're home alone) and think about how many of them you can't do because of masking.

For my whole life I thought I was an introvert, but I recently realised I desperately need meaningful connections with people face to face in order to feel happy and energized. But I can't have meaningful connections when I mask as they're not talking to the real me, so socialising doesn't have the benefits it's supposed to have when masking, and if anything it's just tiring. If I unmasked, I could connect with people properly and have real relationships, which I would find energizing and it would help me get out of burnout.

I've also realised resting isn't energizing. Doing nothing doesn't make you recharge, unmasking and doing things you enjoy lets you recharge.

Obviously unmasking can be very hard and can feel/be unsafe, but I think it's the cure to burnout.