I ended up buying the Alpha through Itch for 15 US bucks. Probably not the wisest financial decision but eh.
Just got into midgame (4th sector), listing down design differences vs FTL:
1. The game is linear roguelite vs the "free roam" of FTL. You move forward from left to right through branching nodes (functionally same as FTL, there are fight nodes, empty one, shops, events, etc) but there is no Rebel chasing you so the dev prolly limit how many nodes you can go on each sector by doing this.
2. No Medbay equivalent. You regen part of your health every time you move node to node. This is probably to facilitate more crew combat focused design. Boarding/being boarded now is a calculated risk as you can't easily recover health. EDIT: there is actually enemy with Medbay, still don't get one in my ship
3. Equipment: you can equip your crew with Weapon/Armor/Misc. Misc items can be Accessory giving bonus or consumeable items.
4. Psykers. There are units that can have default Psyker abilities or there are "replaceable" ones. You can buy new "spells" from shop to replace the power your Psker has (one power per Psyker only).
5. So far I think no drones? Instead you have normal Weapons and Missilies to be different system. So you can equip 4 Weapons and 3 Missilies. This is the biggest design difference I consider to be not good. Drones added so much to original FTL strategy.
6. Setting wise, yeah this is a WH40K clone allright. They changed names like the Chaos Gods' around but it is clear as a day what the inspirations are.