* download the psbt
* in Sparrow: File -> Open Transaction -> File
* finalize the tx and do the normal @npub17tyke9lkgxd98ruyeul6wt3pj3s9uxzgp9hxu5tsenjmweue6sqq4y3mgl QR-based signing
* File -> Save PSBT -> As Base 64
* upload signature to Unchained
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*(note that this approach is kind of dumb; I could have just constructed the entire tx in Sparrow, signed, and broadcast it from there without going through the Unchained UI at all. BUT... in the case where I need them to sign w/their key, I would have to go through their UI so it's good to know the steps!)
I have created my first Unchained vault!
Two SeedSigner (npub17ty…3mgl) keys, plus Unchained's collaborate custody key.
First minor hiccup: for some reason they skip the first receive addr so for a moment I thought my parallel wallet in Sparrow was somehow wrong.
