When trying to deploy ie-arcfurnace (and probably others) capsule, I'm warned 6x Block of Steel are missing, though I have Steel Block from Thermal Foundation in my inventry.

Known issue, I've asked the capsule dev to add a fix. Until then you can chisel the blocks into the correct modes version

I was able to edit the nbt for the blueprints to swap the blocks out, fixed in upcoming version 2.0.0

Oh, I overlooked Lythom/capsule#48.