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Tutorial would be nearly same, just replace BitcoinCash with Bitgold in tutorial.

Hope that helps!

What if I had some BTC on a paper wallet at the time of the fork for BTG? Will that work as well using Coinomi?

And also I had some BTC on Coinbase wallet - how to do it in this case to get the BTG?

You can't claim btg from coinbase, neither they give you access to private keys so your btg are lost.

And for first question try to import paper wallet's private key into coinomi.

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