Thanks for info! I just installed this wallet, it made no problems generating seed while offline. Only potential problem could be that ot doesn't use BIP 44 derivation path, so I'm not sure if it is compatible with other wallets.
It is using BIP39 seed phrase. That is all that matters. You can be able to recover your coins on other wallet.
The wallet is also support Electrum seed phrase if you wish to go for that option. But you posted that you wanted universal one which is BIP39 and it is also supporting it.
I tested the wallet few weeks ago and I added it here also.