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.