I used to join the late Minyanim for Mincha during the week and Friday in 770, since it is hard to get Shabbos prep done and be in Shul early many Fridays. Also, bad habbits are hard to break.
Where I live now, I would have to come on time to the only Mincha Minyan, some time before Shkia. There isn’t even one minyan Mincha in entire city after Shkia.
if the entire city has indeed a minhag/psak to daven before shkia, can Chabad have a different psak/minhag?
Please advise me.
There is a Machlokes HaPoskim if one may daven Mincha after Shkiah. The Alter Rebbe is of the position that we shouldn’t protest those who do daven after Shkiah. This doesn’t imply that it’s the right thing to do LeChatchillah.
Chassidim generally were very particular to ensure they finish Mincha before Shkiah. Notwithstanding the plethora of the Minyanim in 770, this is the right thing to do. There are unfortunately occasionally other minyanim in 770 which are not fully consistent with Zemanei Teffilah.
Even according to the position that one may daven after Shkiah, if faced with a choice of a Minyan after Shkiah or davening without a Minyan before Shkiah, some maintain that it’s better to daven B’Yechidus.
It is well known that the Rebbeim were so particular about this that they davened before Shkiah without a Minyan even when they had Yahrtzeit rather than davening after Shkiah. In the earlier years, the Rebbe did this several times too.
Certainly, in a place which has no such Minyanim this would be a breach of custom to introduce something like this, a matter which is highly questionable. There is a very simple solution to your situation: make it a habit of always coming on time to Shule. Your reluctance or difficulty to change your habit should not result in the community changing their standards and accommodating a behavior which is highly questionable.
מקורות: ראה סידור אדה״ז סדר הכנסת שבת. לקוטי דיבורים א ע׳ 79. משנ״ב רלג, יח. היכל מנחם ג ע׳ רלה. קובץ העו״ב ג׳ תמוז תשס״ח