Opsec of self-custody wallet

Hi all,

I previously posted about using the Keystone 3 Pro for seed generation, but after digging deeper, I regret the purchase. I’ve since learned that its firmware is not fully open-source, and the secure element is closed-source as well. Because of this, I’ve decided I won’t be trusting it for seed generation or signing.

🔄 New approach:

I'm now shifting to a fully DIY, air-gapped setup:

• Seed generation: Using Sparrow Wallet installed on Tails OS (no persistence), offline, booted from a USB.
• Signing transactions: Each time I need to sign, I will:
  • Prepare a PSBT on an online watch-only wallet (e.g., Sparrow on a separate device).
  • Transfer the unsigned PSBT to the Tails machine via SD card or USB.
  • Sign it offline in Tails.
  • Transfer the signed PSBT back to the online device to broadcast.

🔒 My goals:

• No seed ever touches an online device.
• Fully open-source, verifiable signing process.
• Avoid trusting closed-source firmware or secure elements.

Is this a solid and secure approach from an OPSEC standpoint?
Anything you'd suggest to harden it further?

Appreciate your thoughts!