I learned something new in the past week: back in the early days of Bitcoin, coins were sent to pubkeys instead of addresses. This makes it impossible to sign offline using an SPV wallet.

After some fiddling, and after dusting the addresses to enforce replay protection, I used this to extract BCH, eCash, BTG and BCD:

• Install a fresh spare laptop (with VPN of course).
• Download the full client (note: I do not trust this software!)
• Import the pubkey, let it synchronize
• Take it offline
• Import the private key
• Create a raw transaction to a new address (on the correct chain!)
• Copy the transaction to a USB stick
• Broadcast the transaction from another device
• Wipe the laptop (don't let it go online again after you entered the private key!)

I haven't figured out yet how to do this with BSV. Talking about this shitcoin: Coinomi is delisting is on May 1! If you have any funds left there, get rid of it