Today’s times

What do you think about time-dependent mitzvot in places where the times of day are particularly long or non-existent?

Example A –
I traveled in Iceland a while ago. Dawn breaks around 2:00, but the sun doesn’t rise until around 6:00. Is it appropriate to say that all the prohibitions before prayer (eating, driving, etc.) apply from dawn, even though there is still an hour or so until tefillin time?
Example in –
In places where there is sunset but no rising of stars, or no sunset at all – do the time-dependent commandments belong and should they be determined according to a 24-hour clock? The question exists, of course, in a more extreme (and much less practical) way in outer space, or if in the very distant future we colonize other planets.
On the one hand, it is clear that when the Sages defined ‘time to lie down’ and ‘time to rise’ and matched them with times for reciting the Shema, they did not conceive of a reality in which these changes (of dawn and sunrise) did not exist.
On the other hand, it seems that at least some of their definitions rely on verses (at the beginning of the blessings, they rely on “and the sun came and purified” to say that this is the beginning of the night for certain matters, or on the verse in Ezra “the rising of the dawn until the stars appear” to define the day), and if so, it is possible that they understood that the Bible depends on the visibility of the sky, and if so, it would not be possible to observe time-dependent mitzvot in these places (and I remember once seeing the name of one of the rabbis known in the Haredi community – I don’t remember which one – who said that there is a difficult problem with circumcision in northern places, especially in the summer and winter seasons when there is no sunrise and sunset).