This year, for some days in April and in the summer months, the Jama’ah of Ishaa’ at the mosque will be performed combined with Maghrib (Jam’ Taqdeem). This is due to the late Ishaa’ times on these days which make attending the Jama’ah difficult for many in the congregation.
This is an opinion of the European Council of Fatwa and Research, which reads:
The Council confirms its previous Decision no (3/3) concerning the legitimacy of performing the Maghrib and Isha’ prayers together on missing the sign of Isha’ or the delay of its time, in order to save the Muslims living in the West inconvenience and difficulty.Final Statement of the 12th Ordinary Session of the European Council for Fatwa and Research (https://www.e-cfr.org/twelfth-ordinary-session-european-council-fatwa-research)
It has been reported in an authentic Hadith on the authority of Ibn ‘Abbas–may Allah be pleased with him–that the Messenger of Allah–peace and blessings be upon him–combined Zuhr with Asr prayer and combined Maghrib with Ishaa’ prayer in Medina, without being in a state of fear or severe rainfall. It was said to Ibn ‘Abbas: “What did he intend thereby?” He said: “he wanted that his Ummah should not be put to unnecessary hardship.”
People who will be praying at home should observe the actual times of Ishaa’ as long as there is no unnecessary hardship in doing so. That is, people who normally stay up till late should pray Ishaa’ on time. On the other hand, the individuals who might find observing Ishaa’ on time extremely difficult in certain nights may use the same opinion mentioned above and combine Ishaa’ with Maghrib only in the nights when that is necessary. For example, this might apply to schoolchildren on weekdays or workers who have early shifts and need to sleep early.
Allah knows best.