Besides what Mister_M said, Shadow over Meridia also has a domme protagonist, although she is not a very harsh domme and the game is lezdom-only. (and AI art, so it's not for everyone even though I really like it

)
As for most Americans not understanding how feudal vassalage actually worked, meh, I guess add that to the garagantuan pile of historical facts they (and by extension most fantasy universes) get wrong! (alongside all fantasy towns having stupidly-broad streets, the architecture being bleak and colourless af when it should be anything but, women always wielding bows, when in actuality bows, especially longbows, require the most muscle mass and stregth to use properly and therefore real historical female warriors were
least likely to be archers and more likely to wield crossbows or even two-handed swords etc)
I think I just got used to fantasy universes missing a lot of the nuance of how actual historical societies worked, (it's also rare that you even see mercantilistic city-states run by plutarchic "Signorias" like Genoa, Florence, Venice etc, or other republics/trading city-states like Novgorod or north German cities in the Hanseatic league - it's almost always monarchies, and never complicated semi-elective monarchies with convoluted politics like what the Holy Roman Empire had, but always just boring agnatic primogeniture ones where power is so centralised in the hands of the king they look more like 18th century absolute monarchies than any medieval state...

), so that's not a criticism that's often at the back of my mind.
Also fun that you mention "Jus Prime Noctis" in particular as a myth, as I think I remember reading in Engels's "Origins of the family, Private Property and the State" that he believed the custom was practiced in Aragon (Catholic kingdom in northern Spain that included the Basque country) and in a couple other places with Celtic heritage. I'm not sure whether Engels' claim was based on bogus sources, (he was writing in the 19th century after all, and I think he gave some contemporary German historian as his source for that claim, so he might've just been wrong) or whether he was right but this practice (of the liege lord sleeping with the wife of any of his vassal peasants before they did) was only a localized phenomenon in some regions before the 1500s. (like Aragon) This I genuinely don't know, but if you want I'll search for, give you the specific quote by Engels, and you can tell me whether he was full of bullshit on this one or not!

(I'm not one of those doctrinary marxists or anything - even though I agree with the overall ideology and I want a more democratic, classless and stateless society, I recognise Marx and Engels were obviously wrong on some things, such as Marx's horrendous analysis and misunderstanding of Qing dynasty China to give one specific example)
Tbf I'm not that much of a medievalist myself (in fact I sorta disllike the middle ages in Europe as a time of religious dogmatism, sectarianism, censorship, infighting, horrible sanitation and hygiene standards - just read about the "Erfurt Latrinensturz" if you haven't yet, as it's honestly hillarious -, and in general very little scientific and artistic progress. I guess you'd probably expect this from an atheistic communist like myself, but yeah, I pretty much prefer any historical setting, from ancient times to the European renaissance or Enlightenment, over the middle ages) and I would like it if fantasy universes took more creative license and depicted more unique societies that do not necessarily copy the mold of European feudalism. I'd like it if more fantasy books/series/RPGs or what have you took more inspiration from historical systems other than feudalism, such as Imperial China's, Golden Age Islam with its
iqta system, (which wasn't inheritance-based nor included serfdom) or even maybe from how Mesoamerican or South East Asian buddhist empires (like the Khmer or Majapahit) worked.
Alas, as you pointed out, many fantasy games and YA novels (don't get me started on YA novels as I hate them and their simplistic-ass cookie cutter liberal plots with a passion

) don't even get feudalism right, or ever really delve into complex medieval politics like those of Holy Rome, the Papacy or Italian merchant republics, so I'll probably have to wait a few centuries for non-European based fantasy... This compounds though into why my favourite fantasy universe ever is to this day The Elder Scrolls, as its metaphysics and creation myth are part-inspired by Sumerian ones, the Khajiiti cat people get a lot of Indian, Turkish and South-East Asian influence, Redguards get middle eastern, Cyrodiils/Imperials obviously Roman, Reachmen/Forsworn get a combination of native American and mainly Celtic inspiration, and many of the races are such unique blends of both in-game ideas and historical societies they just come off as alien, but in a culturally cohesive way that makes sense! (like the Dunmer, Bosmer, Argonians etc) I really hope Bethesda don't fuck up TES: VI, as they decided to set it mainly in the most boring province of Tamriel (High Rock), and their latest games like Fallout 4 and Starfield don't exactly boost my confidence in their current writing skills or anything...
Anyway, have a great weekend and feel free to DM me if you want to exchange more ideas about fantasy, vassalage, history or whatever, as I just realized I ranted for over 90% of this message on topics unrelated to femdom, so I'll stop here!

Nice to hear from you again Jaike!