Re: A Non-Custodial wallet, Atomic Wallet, being compromised

But they use something "nonstandard derivation" for non-BTC coins and I haven't been able to import the seed into other wallets (Exodus, Trust wallet).

No need to import your seed phrase into other wallets. Create a new wallet and send all your coins to that.
Note that both Exodus and trustwallet are close-source and there's a possibility that the same thing will happen to them.

I personally would not open Atomic Wallet at this time, seems very risky. So importing the seed into another Wallet is a must to send the coins in a safe way.

Greets.

I don't think users that didn't used Atomic Wallet recently are safe as well. I've seen multiple reports of users on Reddit & Twitter that didn't used the application recently and still got hit by the hack. If it was me the second I heard about this I would instantly create a new wallet on a secure environment and transfer all of my funds to it.