Update; I broke the lever on the MT8 and decided to upgrade the lever (price was right) on the MT7’s. I also rebuilt one of the master cylinders in the MT7.
I ordered a couple of new plungers and seals when the MT7’s started to fail.
Was fairly easy to install and a significant difference in lever feel afterwards. (Purchased in 2020?). One of the seals had completely disintegrated, the “O “ ring was worn, the internal spring was fine, and there was no visible wear on the cylinder wall.
I suspect that some fluid was escaping past the seals and causing poor bite point, modulation and eventually complete failure.

I installed a new HC3 lever on the rear brakes for the Rail. Not much difference in the feel but there is some more adjustment. (Not really worth it IMO but the price was right. )

The MT8’s work fine for the hardtail and the lever parts are interchangeable with the MT7s.
Btw; the front rotor is 220mm and the rear is 203mm. The smaller rotor on the rear caused less tire drag and better lever modulation.

I’ve struggled with Magura brake systems over the years but they are great brakes once they are setup and serviced properly.