Sometimes people give me flack because you can’t generate the checksum word offline. But to me this is a non-issue.
At SOME POINT your seed has to touch hardware. That’s the only way you’re going to generate an address to receive funds. Whatever machine that is can also calculate the checksum word and tell you what it is.
IMO, every signing device that deals with BIP39 seed phrases should have last word generation as a feature. Yet few do.