hello99 wrote
“HaRav Moshe Feinstein zatzal writes in Igros Moshe OC 4:105.5 exactly as I have been saying. That one who intends to remain in EY and keeps 1 day YT should NOT wear tefillin Chol HaMoed”
That is a distortion of what Rav Moshe z”l says there. While part of what you wrote is correct, you left out a very important part of the teshuvoh. If you proceed a bit further there, you will see that it says explicitly that one MAY put on tefillin on chol hamoed in Eretz Yisroel now since many moved there from Europe in recent times, some of whom do so.