Digital nomads in Vietnam: what are your favorite work-friendly cafes and hidden gems in Vietnam?

I'm currently traveling in Vietnam and trying to discover great places around the country, in particular in Ho Chi Minh City, Da Nang, Hoi An and Hanoi.

I'm especially curious about:

• work-friendly cafes with good Wi-Fi and power outlets;

• hidden gems (cafes, rooftops, chill places, restaurants, view points, etc.). Something not touristic.

Which places did you really enjoy in Vietnam?