Self custody is the only way. You can buy a nostr:npub126ntw5mnermmj0znhjhgdk8lh2af72sm8qfzq48umdlnhaj9kuns3le9ll server and set up your own Node. This is really a must as you journey down the rabbit hole. Use Sparrow Wallet to manage your BTC. You can then take a further step and run a Bitcoin Lightning Node for payments. Use nostr:npub1xnf02f60r9v0e5kty33a404dm79zr7z2eepyrk5gsq3m7pwvsz2sazlpr5 wallet to manage your channels. Get your BTC off Coinbase. Plenty of help here if you need it.