What planetary combination in a Birth chart and Navamsa gives a marriage with a foreigner?
Before going into the planetary combination for marriage with a foreigner, let me give some background to analyze this particular scenario. In ancient days, people born, lived and died in the same place. They rarely migrate to a different place. Most people marry in close relationship and hence spouse would also be from the same location. There are very rare scenarios when someone would meet and marry a spouse from a distant place. If that happens then it would be called an unconventional marriage.
Due to the industrial revolution, many started migrating to different places. For one who born in one place and studied in other city marrying a girl from different town would no more an unconventional marriage. So the astrological combination for unconventional marriage should be applied to this scenario but taking into consideration of native social background.
That said, Rahu will be the main indicator for marrying a foreigner, not only because of Rahu represents foreigner but also its influence on the 7th house or the Kalatra karaka Venus would indicate unconventional marriage. Marrying foreigner would normally mean that native will settle in the foreign country after marriage, so the 12th lord and 9th lord should be connected to the 7th house or 7th lord. If in case, 4th lord is well placed but 7th lord is well connected with 3rd & 12th lord then native may not marry a foreigner but marriage may happen in a foreign country.
So in summary, the influence of Rahu with 7th lord and Venus would be a primary indicator in addition affliction to the 7th house would indicate an unconventional marriage of any form including marrying a foreigner.
Note: Please don’t blindly apply these rules without accessing the strength of 7th house, Venus and 2nd house.