I would suggest you try BULL wallet. When purchasing off an exchange of your choice, withdraw via Lightning to your Instant Payments wallet in BULL, which will automatically swap your LN bitcoin to Liquid bitcoin (perks of Liquid is that transaction amounts are confidential) and then swap back to on-chain. You can even connect your wallet to BULL wallet, and set automatick swaps from Liquid directly to your cold-storage when your threshold is reached i.e. 1M or 5M sats, it's up to you. Also Bull Bitcoin wallet should be available in Switerzalnd soon, so youll be able to buy Bitcoin directly via Liquid, followed by auto swap to cold stage.

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