On some devices, it's long DOWN button. On devices with Music support it doesn't work by default as Music app is launched instead.
However, you can configure it for a different button, e.g. for…
I know this is an old post but I have a 5 Plus with Music active and when I hold the DOWN button it takes me to my music settings not the watch face. When using Music, does it change the hot key to get to the watch face during an activity? How can you get to the watch face with Music active?
On some devices, it's long DOWN button. On devices with Music support it doesn't work by default as Music app is launched instead.
However, you can configure it for a different button, e.g. for long LAP press. Steps to set it up:
Voila!
I wanted to do the same thing on my Fenix 6X. Access the main watch face when recording an activity, though most of the time I am happy to page through all the screens on the activity until I press Stop and save it.
The SYSTEM menu needed is Hot Keys…
Hold BACK was already setup for Watch Face
That’s the bottom right button on the watch. Just tested it and it works fine. I’ve used the watch for well over a year and I didn’t know this!! But I do now… Just hold the button down and after a short delay you will get the main watch face on screen from wherever you are.
It works on my Fenix5 but it used to take me to my nomal watch face, but now it often takes me to default (First one in the watchface list). I wonder if it is a memory issue now. Watch may not have enough memory. I've added a custom Data field to my activity, can't imagine its too large just single field to tell me how many beers I've earned. Could be the watchface now uses more memory. Not sure.
Sorry but the method described by CraZ_CZ (Czech Republic? Me too : ) there is not an option to assign Watch face to LAP button. But I don't know if it is a bug, hidden or a newly implemented feature, I just by mistake discovered you CAN see regular watch face during activity. All you need to do is go to activity settings (you need to do this for each activity in which you want to view the watch face) and DISABLE the LAP button. Now start the activity and press LAP and voila - your watch face. If you cycle through (as normally with UP and DOWN buttons) all the widgets, it is possible you cut GPS to your activity, but if you just stay on the watch face you are fine. To go back to cycling through the activity screens, just press LAP again.
Okay so there are basically 2 ways how to make this work:
1) System - Hot Keys - assign Widgets (it is really useful to switch to English and find out the name in your languge based on the items above and below, this was problem in my case; also there reallly isn't any Watch face item, may be there was in the past but now it isn't) to the button / buttons you wish.
2) Activity settings - Disable LAP button function in the activity you do and the LAP button will take you to the same place - you lose LAP, but you save one Hot key slot.