>> Transferring their fund by importing the 12 words into other wallets like Electrum might be a good step or any wallets that support importing BIP39 seed phrases.
As already mentioned, this doesn't change anything. You should create a new wallet using a safe tool on an safe device and move all the fund to that.
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.