Cool!! Cake Wallet (mobile) is great, you can have multiple wallet incl. BTC, NANO, LTC.

You can not on-ramp directly to monero, so you create ex. a NANO wallet and an XMR wallet in Cake Wallet.

Go to your NANO wallet and hit "Buy", Cake will try to find the best price.

When you receive you NANO you just hit "swap" and choose your XMR addr. (in the address book icon). Cake will again try to find the best swap price for you. That's it.

So far, I am not relying directly on the DEX/CEX. As I don't do trading, I buy and hold. In the case of monero I also spend a considerable amount on anonymous servers, domains, stuff on XMRBazar etc. I guess you could probably slice the top of the cost by using Kraken or Bisq, but I can live with the additional 5% cost doing this directly from the wallet.