I couldn't find relevant information on this, but I think I figured out a way to answer this question.
We know that Haworthiopsis limifolia, formerly known as Haworthia limifolia is native to a few countries in southern Africa, thus we can check native climate since its germination process occurs outdoors.
To narrow our search we choose a country that's small and has a uniform climate on its territory, Swaziland for example. Usually Wikipedia shows monthly averages (highs and lows) for capital cities, so we check the climate in Mbabane. Haworthia starts its germination process in spring, and spring in southern hemisphere occurs roughly at opposite time than in northern hemisphere. That's why we can look at spring temperatures in Mbabane to determine the range needed for seeds to germinate.
Furthermore, we can easily see that at this specific location average rainfall starts to rise in October, so we can assume that's when cactus and succulent seeds start to germinate.
In conclusion, I say there's a great chance that your seeds will need a daily temperature above 22°C (72°F) and at least 11°C (52°F) during night time.
I also want to add that I've seen on some sites that a temperature of 17°C (63°F) or a range from 15 to 20°C (59-68°F) is required but I think this is just an average between day and night. Indeed, (22 + 11) / 2 = 16.5°C, so I guess my assumption is right.