I heard that since in Yerushalayim everyone keeps minhag haGra, therefore even a guest shouldn’t wear tefillin. When I was there I was told not to even wear them bitzina. I got the impression that this was just for Yerushalayim, not necessarily the rest of Eretz Yisrael.
This year in the US I davened at a minyan that officially wears tefillin although some of the people davening there do not and they sit mixed together with those who do. It is less of a lo sisgodidu problem to not wear them at a minyan that does then to wear them at a minyan that does not. If you daven at a minyan where most do not wear then you should preferably sit separately, I know some places where they sit in the back or the ezras nashim.