Is it permissible to work or reside in non-Muslim countries that are at war with Muslim countries, given the presence of Muslim communities and a job that does not harm people?

Working in non-Muslim countries is conditional upon avoiding temptation (fitna) and being able to perform the rituals of the religion. It is better to seek work in Muslim countries, as the Ummah is in need of these competencies, knowing that sustenance is in the hands of Allah, and money is not everything, and a Muslim may lose other benefits in those countries.