Christian troops in Northern Europe were given Papal dispensation to allow them to follow religious practices properly during the long(er) diurnal cycle at those latitudes. Were Medieval Islamic peoples given similar exemptions (i.e., for fasting and prayer times) for their religious practices? When is the first such dispensation from?
As a similar example, Catholic religious warriors in Northern Europe were given special dispensation for performing their religious practices in the long northern days/nights:
Apart. from such reverses, the crusader castles of Livonia provided secure bases from which the brethren could conduct siege operations of their own against enemies. These could be of quite long duration, and the peculiar problems associated with the lack of daylight in midwinter are acknowledged in a special privilege the Livonian Master obtained from the Pope in 1344. Having in mind the 'hard labours and infinite dangers' of the 'athletes of Christ and intrepid warriors against the pagans and infidels in Livonia' it was decided:
that they be allowed to carry along portable altars for their priests or others, and in proper and decent places before a day is gone or while there is still light, to celebrate Mass.
—Turnbull, 'Crusader Castles of the Teutonic Knights (2) The Stone Castles of Latvia and Estonia 1185-1560'
Modern Muslims in the far north have similar dispensations:
"What to do during the Midnight Sun and on Polar Nights has been a big point of debate for us," says Sandra Maryam Moe, deputy director of Alnor. Her husband, Andrew Ibrahim Wenhem, is the mosque's registrar, overseeing the legal paperwork of marriages, divorces and deaths. "We finally asked a shaykh in Saudi Arabia, and he gave us a fatwa [instruction] with three choices: Follow the timetable of Makkah, follow the timetable of the nearest city that does have a sunrise or sunset, or estimate the time and set a fixed schedule. We decided to follow Makkah for the part of Ramadan that falls under the Midnight Sun or Polar Nights, and then, for the other times, we follow our own sun."
This is echoed in Ruthven's 'Historical Atlas of Islam' in more or less the same terms.
However, these sources don't show when these Islamic dispensations were first introduced. Islamic warriors would have experienced problems on the same scale to the German knights from at least the 13th century on—and traders might have done so previously—in the Rus territories, Volga Bulgaria, and Cuman lands that share latitudes with Terra Mariana (map source):
Note that I'm not saying that the polar night itself was a problem in Medieval times for Islamic travellers/warbands/traders as described in the modern article above, but that the long summer & short winter days would have been. However, even without the polar night, the long days & nights would have been problematic. This would have probably caused problems with at least fasting but perhaps also prayers.
As an example, Vilnius doesn't even have astronomical twilight for more than half a month. Going further north, as into Volga Bulgaria, would be lighter of that level in the winter.
