Weeell, long story short… As in Doctor Who, every planet has its North. So there’s South in Russia.
On that South they consider mulberries to be good for children and birds, but bad for cities and properties/farms (because they’re large and produce lots of juicy and colorful berries which stain). So they consider growing mulberries and selecting varieties as… ehm… somewhat not serious or so.
And that’s exactly what garden nurseries’ owners think about mulberries. Which is why when people eventually decided that they want mulberry plants of exact varieties, none of nurseries had them. But, South, as I said, consider growing them as nothing serious, which is why lots of nurseries decided to sell whatever (seedlings or the only variety they had) under several most valuable names.
And as you might know, Russia is mostly northern country, where growing mulberry is not considered to be possible until recent times. So most mulberry plants in Russian are wild and semi-wild plants with tiny berries which feed birds on streets of Southern towns. And of course on countryside, where noone give them names.
Northern (main, so) part of Russia found possible to grow mulberries only recently. Mostly. So now we are in a stupid situation: we have several names of several selected varieties, but can’t trust to any of nursery regarding true they are or not.
Most mulberry breeding was done in Ukraine, but not for berries. They were breeded in an institute of silk-producing, so they selected the tastiest (for silkworm) leaves 
Now best (for me) part: I live in Chelyabinsk. That’s South Ural (South, but not Southern! :D) - zone 4 more or less. We have up to -35 in winters, snow and frosts come in mid/end October and last until mid/end April, when suddenly comes summer temps. In May we might have either +30 or below zero though. So crazy weather (but I guess everyone from anywhere might say the same about their weather). Aaand… I have found some friends from some Russian places where mulberries are grown. And obtained some cuttings to clone them and plant to my garden. I did so last year, so this is their first winter which will show which of them survive and which not. Also I had a 2016-planted mulberry plant which lives totally fine and gave several first signal berries in 2020. Most of my plants do not have a variety name except the name of the guy who gave it to me. So there are Timur, Eugenia, Oleg, Michael, Roman and other noble persons in my garden. And I can’t wait to meet them this spring. I have about 40 of them and something else too.
I guess there can be more questions. I am here to tell the stories, so please ask. But I know very few about Russian varieties. Probably because I don’t think I can truly find them. Except one.
There’s a variety called Shelly. Шелли in Russian. It came from Ukraine, is large-leaved Morus alba with black fruits of excellent combination of sweetness, sourness and aroma. Should be a dream of anyone, because everybody who has this plant, say that they don’t want to have any other black-berried M. alba. Only M. nigra can be a competitor by taste according to them.
I have a tiny plant of Shelly. But I dunno really if it survives our winter(s). Will see.
