You can use a seed signer to sign with sentinel. I do wish there was a XMR version of seed signer. I dont like "hardware wallets" That store my private keys. Like CC or trezor.
Discussion
I've heard of MoneroSigner but it's far from complete or ready for public use yet.
Also heard stories of some users using two GrapheneOS devices, one meant to be offline and one online for handling XMR to replace a hardware wallet. I mean I don't see why not... but the cost can be pretty heavy. Trezor Safe 3 would involve far less cost for a similar experience.
Yeah, I've had my eye on that project for a while.