I see things about canvas and sprites but I don't know the relationship, and I can't figure out what is a M5Dial call, M5Canvas or what.

In the end I did:

M5GFX display;
M5Canvas canvas(&display);

then followed with:
auto cfg = M5.config();
M5Dial.begin(cfg, true, true);
display.begin();

seems inconsistent but worked.

In my loop I did:
display.startWrite();
canvas.createSprite(240, 240);
canvas.fillScreen(0xABE1);
canvas.setTextColor(WHITE);
canvas.setTextDatum(middle_center);
canvas.setFont(&fonts::Orbitron_Light_32);
canvas.setTextSize(1);
canvas.drawString("The Title", M5Dial.Display.width() / 2, 15);
canvas.pushSprite(0,0);
display.endWrite();

In the rest of my code I always did stuff like:
M5Dial.Display.drawString("To Print", 30, 90);

Are there M5Dial.Display equivalents to what I am trying to do?

The display is silky smooth without flickering now but I don't quite get it.