1.8.1 is widely considered the last version where 90% of classic mods (RSS/RO, FAR, KER, MechJeb) work reliably, while also including the two major DLCs.
"KSP 1.8.1 build 33459 – the unsung hero of KSP updates."
"3. Deployed Science – Plant seismometers on Minmus. In 1.8.1, time warp won't break them anymore." Kerbal Space Program 1.8.1 -33459- DLC
Gameplay clips of DLC parts.
We’ve released patch , a maintenance-focused update following the major Unity engine upgrade. This version significantly improves stability, graphics rendering, and DLC compatibility. Hello Kerbonauts
Hello Kerbonauts!
"2. Moon Landing Replica – Making History gives you the exact LEM ascent engine. Build Apollo 11 with the new terrain shaders." and DLC compatibility.
"1. Robotic Spaceplanes – Use Breaking Ground hinges to make folding wings that actually lock now (fixed in this patch)."