Experiences with insulation composite systems from different manufacturers?

First talk to the company and system manufacturer.

Will the company still exist in 15 years? That wouldn't be a good compromise for me.

Honestly? The damn system crap is just a money-making scheme in the end. If glued and doweled properly, it really doesn't matter what was used. The problems usually come from poor workmanship, not bad material.

Are you speaking from experience? Are you active in the field?

Are you speaking from experience? Are you working in the field?

Experience. I’m “only” active in the financing industry and primarily supported property developers and project developers for larger projects.

For my own renovations, I don’t care about such things either – and so far I’ve never had any problems, whether I used mortar from Sakret, Sto, or even Knauff. You’re just “not allowed” to mix – but you can.
And if you let it slowly sink in that different system manufacturers get their insulation material for some insulation types from the same manufacturer, it becomes even more schizophrenic that you are only allowed to use Sto mortar for Sto insulation, while the 100% identical panel (basically coming off the same production line) is only allowed to be glued with Knauf mortar for Knauf.

But privately, even when doing the work myself, I don’t have the liability issue.

Have you by any chance spoken with the applicator or the sales representative of the system manufacturer in the meantime?

Experience. I am "only" working in the financing industry and mainly supported developers and project planners for larger projects.

With my own renovations, I don’t worry about such things either – and so far I’ve never had problems whether I used mortar from Sakret, Sto, or even Knauf. One is simply "not allowed" to mix – but one definitely can.
And if you also savor the fact that different system manufacturers get their insulation material from the same manufacturer for some insulation types, it becomes even more schizophrenic that for Sto insulation you are only allowed to use Sto mortar, while the 100% identical board (which basically runs off the same production line) at Knauf must be glued exclusively with Knauf mortar.

But privately, even when doing my own work, I don’t have the liability issue.

Have you meanwhile spoken with the installer or the distributor of the system manufacturer?

Hello, according to the site manager this should not have happened. The tender states that everything must be from one system. But functionally he sees no problem because high-quality materials were used. Exactly what you say, it’s the same stuff but packaged differently. The trade offers an extended warranty. It remains unclear to me whether this approval is legally required or mandatory. What are the consequences if no approval is present?

What are the consequences if there is no approval.

The ETICS is defective and requires demolition (or a remedy with individual approval by the responsible building authority). On the topic of defect:

The systems can only be tested as systems, as the name suggests, to determine their structural properties. That means the approval then only applies to the test setup exactly as at the testing institute. Regularly, the applicant for approval is the manufacturer of the insulation material, who purchases the fastening material. Accordingly, this combination must be specified for the approval so that it is recorded in the approval, and the insulation material manufacturer is obliged to continue purchasing the fastening material from the same supplier. The supplier usually gives the material a "White Label," a branding of the insulation material manufacturer, and a part number in their program. The contractor knows which double biscuit is behind this Prinzenrolle, often gets the OEM material from his wholesaler cheaper as "original" or only in this way included in his quantity scale, and therefore buys regelmäßig inhaltlich das exakt identische Zeug with, from a pedantic point of view, an apparently "wrong" order number. Mind you, this is the norm, not just "often." Formally, he thereby releases the "system" manufacturer from warranty and takes it on himself (and puts his clients halfway into the gray zone). That a building authority would demolish a "black construction" because the boards were attached with (allegedly) "wrong" disk dowels is something I have at least never heard of. However, I do not read the so-called newspaper, popular only because of its sports section.

That a building authority would have a "illegal construction" demolished because the panels were attached with (supposedly) "wrong" plate anchors is something I have at least never heard of.

Where there is no plaintiff, there is no judge. I have also already written that personally the "problem" would not particularly bother me.