Which wall structure is meaningfully vapor-permeable?

The process of heat recovery is "technically small-scale" much less efficiently implementable in every single-room mini controlled residential ventilation gadget; I don't even know if the manufacturers themselves don't even see it that way and only offer heat recovery with central systems at all.

Then you are not technically up to date. Decentralized ventilation systems now predominantly come with heat recovery. The one I am installing now (out of necessity, since central is not so easy during renovation) has heat recovery (90% heat recovery and thus also eligible for KfW funding). Additionally, it comes with a humidity sensor, light sensor, and is networked with each other or connected to the differential pressure measuring device at the chimney.

My window frame ventilators are equipped with solar-powered heat recovery, especially those in the south and when the sun shines brightly, [Blende acht].

Then you are technically not up to date. Decentralized ventilation systems now mostly have heat recovery.

I am indeed surprised and would not have expected relevant demand due to efficiency reasons. It's not my area of expertise—as you know, I openly belong to the "don't need it" faction when it comes to controlled residential ventilation.

and networked with each other

Perhaps in terms of electronic smartness, but decentralized systems do not operate with a centrally managed shared air volume.

My window rebate vents are equipped with solar-powered heat recovery, especially those on the south side and when the sun shines, Blende acht smiles.

quick side question:
Where can one purchase the white bench?

as you know, I openly belong to the don't-need-it faction when it comes to controlled residential ventilation.

Or maybe rather to the don't-know-it faction?

The awakening comes at the latest when making a direct comparison.

My specialty is not that - as you know, I openly belong to the I-don't-need-it faction when it comes to controlled residential ventilation.

It's not a problem. Now you've learned something new again ;)