You are mistaking Saṅkhārā for concepts. Concepts are perceived as stable and satisfying. Saṅkhārā means conditioned phenomena. That refers to physical elements and the rest of the five aggregates. All saṅkhārās come under the first noble truth for being deficient, impermanent & conditioned. But there will be no mental suffering if you do not cling to them. Think of it as a fire. You don't get burnt as long as you stay away from it. But that doesn't mean the fire isn't hot.

There's no non-suffering element except for Nibbana.

You are mistaking Saṅkhārā for concepts. Concepts are perceived as stable and satisfying. Saṅkhārā means conditioned phenomena. That refers to physical elements and the rest of the five aggregates. All saṅkhārās come under the first noble truth for being deficient, impermanent, unpredictable & conditioned. But there will be no mental suffering if you do not cling to them. Think of it as a fire. You don't get burnt as long as you stay away from it. But that doesn't mean the fire isn't hot.

There's no non-suffering element except for Nibbana.