I'm sorry this answer is so late but I do hope it helps

I can't speak for all of ancient times though from what I have read and heard, I'm not aware of a general sense of ancient eras being great for gender gap. I do however know something about an era (ancient China, speciality 190-284 CE but also know something of the decades before) without female protest against the system.

It was an era where a woman could not hold government office, bar being ennobled with a pension or similar income, other than being a mother or lover of an Emperor as the default position. Wei Emperor Cao Rui employed a whole six from his harem to handle memorials as if part of his secretariat but this was highly unusual and not seen as a positive.

Mourning periods were longer for a male relative than for a female, education was to help serve the family better. Infant females seem to have been more likely to be left to die (this was not approved of by government), property splits to the children seem to have favoured the males though not insubstantial for a female. A woman with a warrior spirit was... perhaps not seen in the same welcoming way a male with a warrior spirit might be, the male Yang had become superior to the female Yin and failure to assert that from an Emperor brought natural disasters.

Marriage via conquest was not uncommon during the civil war and already being married (or even having a child) wasn't always protection from being forced into bigamy. A wife or concubine could be dismissed if not careful (don't talk badly to a dog in front of stepmother as Bao Yong's wife found out) though a wife could divorce husband but it seems a rarer occasion. A concubine would be under strict supervision and rely on careful rules of who might be allowed to visit while not always able to rely on the husband's loyalty or even support if kidnapped.

A member of the Emperor's harem entered a dangerous hotbed while such a lady could be dismissed, exiled or (usually the version I come across) even killed via "died of grief" aka forced suicide. A soon to die concubine/Empresses wishes for who would care for her child was ignored if the male Emperor wished to it and even coming to term perhaps not always in a woman's control either. If things went wrong for the dynasty and a woman was favoured, the beauty who destroys the Empire trope could be used.

For a male, there were recognized routes up the official career path, none of which were open to females. One could be a respected female for the female virtues or a scholar but to have an influence on state affairs or to see the family through political crises, one relied on the position and willingness of male relatives to listen (or having a very powerful friend). If one survived in a harem and as an Empress (and avoid a misogynistic rewrite of history from a displeased scholar), one could become a Dowager, which could hold considerable power thanks to established ritual and the lady's skills and personality. However only one lady out of the hundreds and even thousands of ladies of the harem could reach that lofty height of Dowager, players could get killed and once one reached that height, any signal of ambition would not be taken too kindly.

You do something significant, worthy of the history books... you have less chance than a male would. Not every male of significance gets full records, not even a Chancellor thanks to the degradation of time, politics of the court or the writer and so on. However, for three kingdoms females, the primary source of the era from Chen Shou has 65 volumes and only three go to women. Empresses only and one for each of the factions (Wei, Wu, Shu-Han), no females outside of that getting their own entry and often with no personal name. Some were brought to light by other works of history, a family history surviving to be added later here, Huangfu Mi's work being added by Pei Songzhi as an annotation there brings us figures like Wang Yi and Xin Xianying. Later works from Fan Ye's History of the Later Han and the Jinshu sometimes cover figures in the early and later stages of the era like Cai Yan or Zhang Chunhua that Chen Shou neglected.

Even those that were granted a whole biography can find their political achievements downplayed, their usefulness as a political adviser reduced to one line. Like Cao Pi's wife Lady Guo who helped him gain the succession but whose advice we do not get even a glimpse of. Those that weren't covered and for whom we get mere fragments are figures like Sun Quan's tiger daughters Luyu and Luban who were major political players in the court of the Wu dynasty. Or Quan's sister, mentioned by Zhuge Liang as one of the two big threats her husband warlord Liu Bei faced and feared at one point. Sadly the famous novel Romance of the Three Kingdoms would, over a thousand years later, further downplay such ladies achievements.

We have certainly not solved the gender gap since those times, pejorative language towards female leaders certainly exists for example, but I don't think it can be argued that such a time was better on this issue. Not with "died of grief", not with woman very much placed as second to the male, unable to serve in roles that males held simply due to their birth.

So if things were so bad, why are there not tales of revolt and female uprisings across the land? We do have a female-led... uprising in the three kingdoms. Zheng Jiang, or Ladies Zheng and Jiang, rose up around the Dongping area in 210 and were quickly crushed. We don't if one or two people, we don't know why or how, the term bandit is used but that can just mean outside recognized authority.

How do we know of this?

A dream.

Yes, a dream. A local figure Liu Zhen (male) had a weird dream of a snake with legs and sought out the dream interpreter Zhou Xuan (male) who explained it. The tale isn't about the female rebels/bandits but about the skill of Zhou Xuan, who would serve the Wei court, that is the only reason we know of this revolt. Though the nature of the dream also sends the message of how unnatural this female revolt was to the "natural order".

I have no idea if this was just a complete one-off event or in other areas of China during the decline of the Later Han and the civil war of the three kingdoms, other females rose up and were quickly put down. I don't know what went on behind the scenes in homes, who braved the potential social costs of loud protest or who quietly tried to alter things in their circles for the next generations. It simply wasn't recorded most of the time, we have to be aware of who wrote the texts and what they deemed important and what was unimportant.

If you rely on protests and the like as proof of the gender gap, you are relying on the (usually male) chroniclers of the time to deem these matters important. Or that the works that mention such events will survive through centuries. Or that the route you see as best for change is the same that ladies back then, in the circumstances and cultures they were in, would also see as the best route for making things just that bit better.

It is true women did incredible things, we know Wang Yi fought in battle, we know of political giants like Lady Wu, a poetess in Cai Yan, scared a future Emperor like lady Sun, tactical advice from Lu Bu's unknown wife, a historian in Ban Zhao. Women who sacrificed and made brave decisions like Lady Huangfu choosing death over re-marriage or Zhao Yuanjing choosing to be executed so her husband could raise their son. It is important to highlight these figures and other women because they can get hidden away and people can underestimate the importance of females in history. That isn't to say, though they made their mark, they weren't all dealing with systems that went against them simply because of they were born female rather than male.

Was there unfairness in ancient times? For the era I cover, yes yes and I'm afraid to say again, yes. There might not be protests that show it but we can look at other things as to if there was a gender gap. The language used about females in power, the scholarly lies, what positions they could and couldn't hold? What glimpses we get of their treatment, what did the cultural traditions say, expectations around the two genders and what was allowed? What was recorded and by whom? Those sort of areas might be better ones to look at when investigating gender gaps of the past so you can compare to the present.

Feel free to ask any follow-up questions and if you have none, have a great week

Sources:

Women of Later Han: Ideals and Reality by Rafe De Crespigny

Empresses and Consorts by Robert Cutter and William Cromwell