Repointing natural fieldstone - which mortar

Hello dear community,

we have acquired a farmstead from 1904 and are currently in the process of renovating/modernizing parts of it, including the exterior joints. These need to be partially renewed, depending on the direction the wall faces and how the weather has affected it. Our joint renovator wanted to use quick-mix (cement mortar).
This does not necessarily have to go wrong, but with old solid bricks, presumably field-fired bricks, there is an increased risk that either the joints will crumble again or even the brick will be damaged? Due to different strength and moisture absorption?

I have done some research and identified lime mortar alternatives such as air lime/shell lime and trass lime mortar, e.g. gräfix 55 coarse, as better options. Spontaneously, I would be in favor of the latter, it is already pre-mixed and costs about 9.00 EUR per 30 kg bag, which should yield 20 liters of ready-to-use mortar.

Does anyone here have experience?
I will try to reach the architect tomorrow. Unfortunately, this has been somewhat difficult lately.

Yes, I have experience with listed buildings. Your suspicion is correct, lime mortar is softer, use that, not quickmix.

Thank you for the response. Would [Trasskalkmörtel] be an option? Apparently, opinions differ on that as well. [Solubel] was also recommended to me, but there is no distributor within a 150 km radius and therefore I hardly believe I will find a [Verfuger] who works with this product. For example, our [Verfuger] was not comfortable with [Muschelkalk], supposedly too complicated.

Through trass, mortar becomes waterproof.
Take it.

Thank you very much for the feedback again :)