I did one partial play-through with Alpha 3.

I have several observations, potential bugs etc. I'll start with an annoying "bug" I'll call it. You cannot, as far as I can tell, destroy an existing building. I also noticed that when you are upgrading say a Research center to a Research academy and click cancel, the building is destroyed and the academy "greyed out icon" is still on the map but with the FULL build time not the upgraded build-time. If you cancel this process the square on your planet is rendered empty.

You cannot re-route a ship mid flight. Any alterations to it's path happen after the ship reaches the destination, so I end up exploring 1 square at a time so I can change direction with my left-over movement points if I see an area of interest. THIS IS TEDIOUS.

You can still accidentally colonize the same planet twice. I have done this with move commands that compound at the colonization. I just cancel the 2nd one to avoid any problems.

Observations:

The Shipyard is VERY vulnerable. So much so it cannot be defended. Except for surrounding it by ships. I would suggest that a player can have a shipyard once they have a starbase sponsored by a planet. The starport is tethered to the starbase and shares it's defenses. A shipyard should also be closer to a planet. Connecting it over larger distances is kinda stupid. It should be within 1 space of a starbase and the starbase can be connected by up to 2 tiles or something.

Starbases designed to push borders, harvest resources etc. are an entirely different beast than a starbase designed to facilitate orbital industry in the form of manufacturing of ships.

Currently I can spam shipyards and spam constructors so I have shipyards galore and starbase galore quite quickly. Space infrastructure should be developed and planned not spammed. It takes a lot of resources to conduct industry in space. EVEN if say we argue that nanites build shit they still need raw resources, personel, power, and time.

When I put star freaquency to abundant and planets to the 2nd highest and then habitable to occasionally I literally had only 12 habitable planets in a large galaxy. Most of these had a population limit of 5-6

We should be able to upgrade through tech our starting building. it is the only building that cannot be upgraded. It can be the vehicle through which we specialize a planet's production. It can be changed but takes a long time, augmented, modified etc. Keeps specialization and customization localized into one building to a degree and keeps it simple and fun.

Events can also focus around these founding buildings on our colony worlds. Random events can give a planet a bonus, penalty,  etc. our choices can influence these changes as well.

I'll do another play-through in a while and see what else I see and perhaps take the game a bit further.