The easiest and fastest for me is the official app (iPhone in my case). Once the file is loaded onto the iPhone, the recording can be viewed without connecting to the camera. There is also viewing software for the PC.
If you use the photos on Facebook, they automatically become a 360-degree video. For videos, YouTube is recommended.
The coolest thing, of course, is to view it with an Oculus Rift or HTC Vive. For this I use "Virtual Desktop" https://steamcommunity.com/app...
Of course, this is also possible and easy with a CardBox or other mobile VR glasses.
But the whole exercise and viewing thing is still a bit fiddly and still has room for improvement...

Unfortunately, not without using a corresponding service. On Android, for example, the Photos app can be used for this. You drag the pictures from the camera onto the phone, the app syncs the pictures into the cloud and then you can share the picture, or an album, as a link via Whatsapp. The link then takes the other person to the web view of the album and they can view the picture in 360. Alternatively, it also works directly via Facebook or apparently also Flicker.
For videos, I can only recommend Youtube so far.

Unfortunately, the process is still a bit cumbersome for both pictures and videos.