Hi, first of all thanks for your work, it's obvious that this game was a project of love and ambition, not something solely made for profit. I had a chance to play in this free weekend, even though only for a few hours and something like 80 turns. It was mostly enjoyable, but not enough for me to buy the game, though that could've been different if I had more time to play. Seeing that the devs are actively gathering and engaging with feedback, I thought it would be good to give my impressions 

As a somewhat experienced 4X player, but without any knowledge of previous Endless 4x games, I started with UE and enabled Advanced tutorial. The game is aesthetically very pleasing, and the UI is mostly legible. Yet sometimes I felt these were conflicting, ex: in System Management Screen, I think planets occupy more than they should, and this leaves very litte space for the building construction queue at the bottom. And there are simply too many things squeezed into the bottom row, maybe the right part of the screen could be utilized for some of these features. 

Sounds & music were generally nice, yet musical changes which accompany some pop-ups were too abrupt and distracting to me. Maybe they could last a bit longer and transition to the normal music could be a bit smoother.

Going into the core mechanics, I should say I really liked how politics is modeled in the game. It is neither a superficial distraction without any real effects, nor a tedious feature that forces micromanagement. It is just at the right level of complexity, and I hope you don't fall into the trap of thinking "more complex is better" like many other strategy games do.

That said, I just couldn't find myself immersed in the technology tree (or circles, idk). Being able to choose between alternatives is generally welcome, but here it was tiring rather than liberating. Sci-fi games suffer in this area compared to the historical ones, since the technologies themselves are not revealing much to the player intuitively. On top of that, I found some things counter-intuitive, like hull unlocks not being located in the military area. I think the game would benefit immensely if techs were a bit more streamlined, and majority of complaints&criticisms I came across on other platforms were focused on this.

Expedition, colonization and system management mechanics are solid. One thing I would like to see would be separation of building and ship construction slots. Hangars may act as the place for the latter, and they could also house relevant upgrades like shipyards etc. Admittedly this would require a major rebalance, but still I think it would add more diversity and control.

Quests and events are generally well designed and interesting. A minor complaint, and this is probably faction-specific, would be lack of on-map representation of some quests. It was weird to read about a massive rebellion that causes the emperor to have many restless nights, without seeing any rebel fleets or whatsoever. Also, it would be better if the texts were loaded instantly (forgot the term for this) or much more faster on pop-ups. It could be that there was an option for this and I missed it, but I remember going through the menu.

This is very subjective issue, but the game includes one of the least liked features for me, i.e. the ship designer. I never understood the appeal of such micromanagement in 4x, I believe such stuff is much more fitting to games focusing on the tactical level, but as I said this is highly subjective, and I know this is a must for many. Anyways, I haven't played enough to see whether manually designing your ships is obligatory to succeed, I hope it's not. Auto-design and auto-upgrade features were very much welcome for me, but it seems that you have to auto-upgrade your designs everytime you unlock a new module. Maybe changing that to act as an on-off option would be better, so that designs remain up-to-date.

As far as I know (or read), only one fleet can engage in a battle, therefore it is not important whether you have total superiority in a system with a couple fleets when enemy has one stronger than any of your individual fleets. I know that's the point of researching for command points, but maybe having a reinforcement mechanic would be good. So that even if other fleets do not engage in the battle, they may inflict penalties on the enemy. Ex: having system superiority could give penalties to movement (representing restricted maneuver space) or accuracy (more ships on the radar) of your enemy.

Heroes also seem to require a bit more micromanagement than I usually like, but I guess they are a hallmark of Endless series, so cannot complain about that.

Diplomacy seemed good, but AI was a bit too unfriendly, so my interactions remained limited. Additional tooltips may be added for attitude to numerically show the influence of your actions on their stance towards you. 

I cannot pinpoint this, but the game lacked a hook for me, something that keeps you on your toes and gives that "one turn more" feeling. When you play Civ5 for example, once you met two-three civs on your continent, the game becomes visible competitive and addictive until one establishes dominance, even if it's your very first campaign. Even when I was losing in ES2, I always felt at ease and the campaign map/galaxy seemed lifeless. It is possible that I just rolled a boring start, and the same applies to all my impressions above. Things are bound to be very different in subsequent playthroughs, and with different factions, but I still think first-impressions are important, especially considering the impatient nature of today's gamer. Nonetheless, the game is still very promising, even though I haven't bought the game, I will be sure to follow its development from now on.

One last thing to add, though this is probably more about Steam's business practices than yours. While freeweekends are nice and all, I don't think strategy games benefit from them as much as others, since they require much more investment. So rather than having a free-weekend, what about something like a free week in the future, with maximum playtime restricted to sth like 8 hours. Well, that sounded a bit like reinventing the wheel, just having time limited demos would also work I guess. 

ps: I forgot to mention this, but lack of an active modding community also pushed me away a little bit. What little appears on the Workshop seems to be very basic stuff. I see that modding is officially supported, but maybe providing advanced tools, having competitions with rewards etc. would attract modders.