Let's take Thomas, a Frenchman, who is moving to live in Ho Chi Minh City for three years.
Before his departure:
🇫🇷 French SIM
He keeps his historical number.
He simply disables data roaming.
Upon his arrival:
🇻🇳 Temporary eSIM
He immediately gets Internet access.
A few days later:
🇻🇳 Permanent Vietnamese number
He chooses a major operator and properly registers the line with his passport. He then uses this number for his local services.
In his apartment:
🏠 Fiber + Wi-Fi
And if his fiber goes down:
📱 4G/5G tethering.
He thus has three levels of connectivity:
French SIM → backup and French services
Vietnamese SIM → daily life
Fiber → home and work
This is a very robust setup for a long-term installation.