I gave version 2.6.35 a try and liked the general idea of the mod very much. I have some things I found a bit lacking, apologies if they were already addressed in later patches. I am playing with space age (only dug to the 3 planets besides Aquilo so far, nothing more) and build a factory in the middle of the map, rails connect to the long tunnels in the 3 directions. I am playing without collapse or darkness infestations.

1. The small ore patches are very limited for trying to build a decent factory. I already turned up the resource level a bit, but it still feels like an annoying chore to move the miners and train stations constantly. This might just be because I am not playing the "intended" way of constantly digging instead of digging for caverns or POIs and then exploiting them. A potential idea I had was to rework how ores spawn: have low yield ore patches "lead" to larger caverns with rich ore fields that are worth exploiting with proper, less temporary infrastructure. Or add another POI entrance type that leads into such a cavern that stays open forever or requires some upkeep to keep open. Or have enemies constantly attack anything build inside, maybe with escalating challenge to make it a tradeoff between resource gathering and keeping defenses working.
2. Spawning Behemoths right in the face of the player when breaking rocks is pretty annoying. It is easy enough to counter by creeping turrets and bringing found/bought Spidertrons along, but it gets old very fast. Maybe there is something I am missing here.
3. Rocks can be destroyed by explosions, e.g. explosive rockets. This generates terrain, but doesn't trigger any effects like biter spawns or POI discovery. I found myself using rockets to dig to get to the space age planets so I don't need to deal with Behemoths. If breaking rocks with explosions would still trigger events, this might also somewhat alleviate 2. as just spamming rockets from a distance is less annoying than walking up to rocks with a pick and getting a Behemoth to the face. Overall some way to dig more effectively or faster would be great, especially if it could be automated.
4. Once you dig out a base and solve power, the base is completely safe from attacks. An incentive to properly defend a permanent base would be great, maybe random events that open up more rocks around the base, possibly with a short warning could be an option.
5. It is pretty nice to farm spawners for ores to get a trickle of resources, but I didn't see any kind of automatic pickup option in the mod. There are mod options, but the idea seems to be to integrate other QoL mods into this one and this seems lacking.
6. Having a way to reduce evolution would be great, e.g. via a found single use item or a very expensive shop purchase. Maybe this is already implemented and I didn't find it. This again might help with 2. by giving limited time with lower evolution to dig while only getting smaller biters.
7. Researching stacking turns all existing inserters into stack inserters, breaking existing setups until their stack size is manually forced back to 1. I would much prefer to have dedicated stack inserters instead of every basic inserter stacking items and waiting to get a full hand.
8. It seems unlocking the other planets' technologies needs space science, which comes from a space platform best I can tell. It feels wrong to launch a rocket through the cave ceiling, maybe there is a way to remove the need for rocket launches to fit the theme more.
9. Shop interactions could do with an automatic way to trade. Maybe have a chest/other structure that does automatic trades and just provides the coins as items. It could be throughput limited and only have limited amount of it, e.g. in the center of the map or by purchases. This would help with voiding overflow or farming coins for Spidertrons or Power Armor instead of having to manually sell entire inventories.

Overall the mod is very fun and a fresh experience, keep up the work!

Thank you very much for taking the time to play the mod and write such detailed feedback. Reports like this are extremely valuable to me because they help me see which parts of the gameplay need more work, improvement, or better balancing.

Many of the issues you mentioned are real, and I’m already working on several of them. I’ll carefully review every point you listed and try to address the problems one by one.

The mod is still relatively new and needs more development before everything is fully completed and polished, so I appreciate your patience while I continue working on it. Thank you again for testing the gameplay, identifying these issues, and sharing your ideas with me. Your feedback is genuinely helpful!