I'm having a similar issue. I have siblings- one from Russia-Poland and one that says German-Polish. I only have the German one on here as "Germany" because some census records simply listed Germany, and I added her before I ran across the German-Polish record. That branch one of the areas I'm focused on right now. I'm leaning toward marking them as Poland because I know the family identifies as Polish, not German or Russian.
I could see choosing Russia, due to the fact that it WAS Russia at the time, but I can also see Poland if the family considered themselves Polish, as there were resistances to Russian rule ( see https://en.wikipedia.org/wiki/January_Uprising
My branch has always considered themselves Polish, even though we don't know much ancestry before immigration to the US around 1860-1880, even though there wasn't a Polish state in the 1800's.
I'd be interested in other opinions for how to properly write it. While there can be notes in the description, differing countries may lead to duplicate profiles and missing out on an oppertunity to link to other family.