Some Soviet authors still seem to be pretty well regarded. Isaac Babel's Red Cavalry stories, for example.
And then there is Michail Sholokhov who got the Nobel Prize in Literature 1965
"for the artistic power and integrity with which, in his epic of the Don, he has given expression to a historic phase in the life of the Russian people".
Quiet Flows the Don was written from 1928-1940, so during Stalin's reign.
To get back on the topic of Nazi SF, here is what I could find about their "SF-literature":
1. Der Mars greift ein (1934)
“The Mars intervenes” is a fascinating Nazi sc-fi novel written by Titus Taeschner, a German engineer who penned two other works of technical science fiction in the 1930’s. A novel that revolves around Professor Sieger, a German scientist and the world’s most famous Mars researcher, who conducts his work in secrecy at Villa Marsberg. After splitting the atom, Professor Sieger is equally successful in establishing contact with the inhabitants of Mars. In time, he learns “all the fast-forward-evolved techno-secrets of the future.” Fortunate for him and the Third Reich, as Germany not only faces European rivals, it is being threatened by a bellicose Russo-Japanese alliance! Somehow, the Martians intervene in earthly events and secure the peace for Germany. And Professor Sieger? After being kidnapped from Villa Marsberg and held on a Japanese battleship, he is freed and eventually removes to Mars.
The name Sieger translated means Victor.
2. Im Jahre 2000 im dritten Reich. Eine Schau in die Zukunft“ by Edmund Schmid (1933)
“In the Year 2000 in the third Reich. A look at the future.” was written by Edmund Schmid in 1933. Here is one translated part:
" (...) this focuses on a great arian festival (...) the birthday of Hitlers successor, the "noble" Herr König whose one hundreds birthday coincidentally falls on in the year 2000. Since Herr König lives as a strict vegetarian, abstains from alcohol and smoking, enjoys as much fresh air as he can get and plays with his German shepereds just like Hitler did, he looks very healthy for his age (...) The Reich in the year 2000, that Herr König rules, has established itself as one of the four big world powers besides England, Japan and the USA.
Almost all German countries, like Holland, Austria, Skandinavia and the German Swiss are now parts of this great prospering nation. France on the other hand is reaching the brink of collapse due to (verniggerung/niggersiation/racial degeneration) while Russia's Red army was able to purge the Jews out of the Union, but is still suffering from the effects of the soviet yoke."
The name König translated means King.
3. Sun Koh – Der Erbe von Atlantis (1933–36)
“Sun Koh-- The heir of Alantis” is a sci-fi dime novel series which was written by Paul Alfred Müller from 1933–36.
The first volume a man lands, wearing only a pajama, with a parachute in London - Sun Koh, the (bronzehäutige/tannend) prince of Atlantis. He is the last survivor of his lost continent and has a great responsibility: because according to ancient prophecies, Atlantis will reappear from the ocean. He only remembers that the has to visit he Excelsior Hotel in London. There he meets two people who he will join him to become his faithful companions in his many adventures, the often outspoken elevator boy Hal Mervin and the undefeated heavyweight boxer Jack Holligan, a black man from the tribe of Joruba who rather wants to be called from now on Nimba. And he meets his arch-nemesis, the Mexican Juan Garcia, from whose hands Sun Koh needs to free his secret love Joan Martini. The spurned Lady Houston is also often responsible for unpleasant incidents and more than once Koh has to save Joan Martini from her envious clutches.
Sun Koh find out that Garcia is responsible for the deaths of his parents and that Garcia has a a twin brother, the eccentric, but good Manuel Garcia.
The twin lives in the so-called sunshine city of the Maya on the Yucatan Peninsula,. There he has found a huge stock of precious Mayan relics.
Manuel Garcia grants Sun Koh access to them after he learns to trust him. Sun Koh is now financially independent and can gather scientists together from around the world who can help him with his invention, when Atlantis re-emerges from the waters.
During his many adventures Sun Koh always finds hints and mysterious buildings, suggesting that some of the Atlanteans had survived the sinking and settled in other continents. And as to the very end, Atlantis rises again from the waters, Juan Garcia is once again ready to snatch Koh's legacy, but with the help of his friends Koh can defeat Garcia. He, together with Joan Martini, enters the as the first humans the reborn continent Atlantis.