What is the ruling on Muslims in Belgium separating due to the lateness of the 'Isha prayer, and is it permissible to combine 'Isha with Maghrib for a long period, or to estimate the time of 'Isha as an hour and a half later?

Our religion encourages unity and warns against disunity. The differing forms of the single prayer within one country are considered manifestations of disunity and fragmentation of the word. The community must reject this and return to what the people of knowledge deem closer to correctness.