Oh wow, that would pretty limiting. Thank you for that heads up!

I see that from the 400 miles altitude they filed with the FCC, you'd expect them to be able to provide maybe an extra 2 hours before + after sunrise/sunset near the equator. However, that appears to improve to almost 4 hours at 50 degrees latitude - assuming 30 degrees of elevation is sufficient for the light to not get too scattered through the atmosphere. If you assume a much more conservative 60 degree elevation requirement then it would be 3 hours before+after sunrise/sunset at 50 degrees latitude.

It also depends on the season, but this has a much smaller effect than latitude.

Shortening the night by a combined 6-8 hours might be quite useful for operations in Ukraine which occur near 50 degrees latitude.