I’m a misnagid of Litvak and German lineage.
But I was a member of a shul that was a merger of a Nusach Lubavitch and masnagid shuls.
They had agreed to follow the Nusach Lubavitch (they were not Chabad or Hasidim) and put the Misnagid name first in the new (1952) synagogue name.
I always davened Nusach ashkenaz wearing ashkennaz tefillin.
BUT, it I davened for the amud, I had to daven from the Tehillat HaShem siddur according to the Lubavitch nusach. I had no problem doing so