I dont think a phone can run a full node of a chain. So I don't think staking via full node is possible. Maybe Im wrong, but you can do it by delegating your token to another staking address lets say eth, bnb, solana, cardano trx and pretty much PoS coins have a feature called staking your token into another node.
Its pretty much same all you need is non custodial wallet go to staking feature and click delegate, a note that some node have different criteria Like their profit sharing APY and other.
Not a full node, but rather a pruned node. Much easier and faster to set up than a full node. If it can be done on a low-powered computer such as a Raspberry Pi, then doing it on mobile devices should be a no-brainer. I understand pruned node aren't the same as full nodes when it comes to supporting the Blockchain network. But at least, this approach is better than just running a light node and "delegating" your coins to other third-parties. Doing everything on the device itself would be a big boost towards the decentralization of the Blockchain.
Developers can make such a thing possible. It's just that they're too focused on "memes" and other speculative trends. The industry has moved away from its utilitarian aspect long ago. But who knows? Maybe someone who values true decentralization will make this happen. Only time will tell...