Is it permissible to combine the Maghrib and Isha prayers in an advanced manner (Jam' Taqdim) throughout the month of Ramadan if the Isha prayer is performed very late, and is this considered a removal of hardship, and what is preferable in this case?

The fundamental principle is to perform each prayer at its legally designated time. It is not permissible to offer the 'Isha prayer with Maghrib for the reasons you mentioned, based on Allah's saying: {Indeed, prayer has been decreed upon the believers a book [i.e., obligation] of specific times.} (An-Nisa 4:103). The majority of scholars do not permit combining prayers while at home unless it is due to rain. However, some scholars hold that it is permissible to combine prayers while at home due to necessity and hardship, provided that it is not made a regular habit. Ibn 'Uthaymeen holds that if the twilight (shafaq) does not disappear until dawn, or disappears for a very short period, then the time for 'Isha prayer should be estimated based on the nearest countries. But if it disappears for a long period and waiting is difficult, then combining prayers is permissible to avoid hardship. The more preponderant view is not to combine prayers in this case as long as there is sufficient time for the prayer, in order to align with the texts and the general consensus of scholars. As for one who is overcome by sleep, they should perform the prayer upon waking up.