First let me say that I mostly enjoyed humankind. The graphics are nice and I love the region system from Endless Legends. Here is some feedback from playing the closed beta:

Fleeing from combat often results in goose hunts. Armies fleeing from combat should be punished, for example by loosing health (like in Endless Legends). Armies can also move way too far when fleeing.

"Show/hide the tile output" should highlight resources which are already exploited. For example with a highlighted border around the resource icon circle, or using transparency similar to when a city is selected. However, the transparency difference between exploited and not-exploited resources in the city view is too weak and it's hard to see the difference.

Culture changes happen too often and it's hard to form a connection with the culture. Often there is hardly enough time to build an emblematic improvement or unit. I would suggest to provide more choices when entering a new area: change culture (as before), upgrade your emblematic unit (at most once), choose a flat bonus based on your current culture (for example +5% science when you play a science culture).

Sometimes region borders have "snake"-like appendixes which feels out of place given that most regions are quite uniform in size. It looks like the algorithm to determine region boundaries could use a bit of tweaking. For example ignore non-cliff boundaries more and try to place boundaries more on cliffs or mountains.

It would be more interesting if region size would be less uniform. For example region size could depend on the total amount of food (or total FIMS) available in that region. Fertile regions should be smaller and barren regions larger. In real countries it is more typical that region size follows population density.

In my playthrough I declared war against a country (AI 1) which had a vassal (AI 2). When I won the war against AI 1 I made them my vassal. His vassal (AI 2) automatically also became my vassal without me ever fighting with them. The game went on for many terms and AI 2 became the second most powerful player after myself, paying me an insane amount of money (2000+ gold) per turn. They never even considered to revolt, or terminate their vassalage. It's especially strange as they had the archetype "traitorous".

Many UI elements are too big especially on a large screen it would be nice pack information a bit more densely.

Choosing regions after winning a war is a bit hard. It's quite hard to see which regions I am choosing. Especially as region names are not displayed very prominent. Would be good to get a preview of what is chosen on the map.