Unfortunately, it seems like Lunu's 24-word BIP39 recovery phrase uses its own unique derivation path and there's no documentation about it.
I tried to restore my test wallet using common paths and none generated the correct receiving address.

But luckily, the Wallet Import Format (WIF) private key is the pair of the receiving address.
You can export that using BitMaxz's instructions and import it securely using Cricktor's suggestion to use Tails but using the WIF private key.

If you can "risk" the amount and think that your system is safe (like what you usually do), you can just import it to Electrum via "Import Bitcoin Address or private keys" in new wallet menu.
Then paste the WIF private key with the prefix p2wpkh: ; example: p2wpkh:L3BxN68HQp7zUv89ifFNDebU......
The choice is yours.