Thanks, for the suggestions, but unfortunately both Unstoppable Wallet and Mycelium are mobile apps and I wasn't able to find any indication that crypto.com desktop app supports BIP-39 passphrase, just tried installing it and it only accepts the seed phrase when recovering wallets.

So the question is still there whether there are any open-sourced alternatives to Coinomi that will fit the bill.

Sorry, forgot to mention another key requirement which is being a desktop app (or at least browser extension) that can be run on Linux, so Unstoppable Wallet doesn't fit under that requirement.

Can anybody recommend a desktop software wallet (that can run on Linux) that natively supports BIP-39 passphrase ("13th/25th seed word") and multiple blockchains at the same time (at least Bitcoin and Ethereum)?

Most of the hardware wallets like Trezor or Ledger support passphrase, but the only software multi-crypto wallet that I was able to find with passphrase support is Coinomi which is closed-source and has a bad reputation. The rest of the software wallets seem to be Bitcoin-only or Ethereum only (like MyCrypto).

Edited: added that it needs to be runnable on desktop, not a mobile app