إن الذين توفاهم الملائكة ظالمي أنفسهم قالوا فيم كنتم قالوا كنا مستضعفين في الأرض قالوا ألم تكن أرض الله واسعة فتهاجروا فيها فأولئك مأواهم جهنم وساءت مصيرا
Indeed, those whom the angels take [in death] while wronging themselves - [the angels] will say, "In what [condition] were you?" They will say, "We were oppressed in the land." The angels will say, "Was not the earth of Allah spacious [enough] for you to emigrate therein?" For those, their refuge is Hell - and evil it is as a destination.
— Quran 4:97
إلا المستضعفين من الرجال والنساء والولدان لا يستطيعون حيلة ولا يهتدون سبيلا فأولئك عسى الله أن يعفو عنهم وكان الله عفوا غفورا
Except for the oppressed among men, women and children who cannot devise a plan nor are they directed to a way - For those it is expected that Allah will pardon them, and Allah is ever Pardoning and Forgiving.
— Quran 4:98-99
ومن يهاجر في سبيل الله يجد في الأرض مراغما كثيرا وسعة
And whoever emigrates for the cause of Allah will find on the earth many [alternative] locations and abundance.
— Quran 4:100
These verses establish that:
Migration is obligatory for one who is weak and unable to practice his religion because of oppression
Allah will refuse to accept any invalid excuses made by people in this regard
However He will accept valid excuses for those truly unable to migrate. Such excuses include disability, disease, imprisonment etc.
Hence such a Muslim should to migrate to a Muslim country. If he is currently unable to migrate then he\she should slowly prepare to migrate and gather the needed resources. Also he\she can consider temporarily migrating to any other location within the hostile country where he\she can practice his religion.
As for "Poverty" there have been cases in Islamic history where poor people have managed to migrate. However if one is truly very poor and can not migrate despite his efforts and desire, then it might be accepted as a valid excuse. Some exegetes have noted the lack of resources among the valid excuses:
لا يقدرون على حيلة ولا على نفقة ولا قوة للخروج منها
— Tafsir al-Baghawy
عن السدي: الحيلة: المال
— Tafsir al-Tabary
Taqiyah or Martyrdom
If some Muslims are unable to migrate then there are two options of dealing with such oppression during their stay in the Dar al-Harb:
They can pretend to disbelieve so that they will be left alone. This is permissible.
They can refuse and accept the consequences whatever they may be. This will earn them reward from Allah and is more virtuous.
See Leaving Islam because of fear and Taqiya - conditions and goals?
It is also permissible to fight back.