I was used this manual to create 3mx for web https://docs.bentley.com/LiveContent/web/ContextCapture%20Help-v10/en/GUID-FEED2A71-66F5-4042-95E8-0DA2D827E21D.html
I got 3mx for web, but not clear what next step?
I need share this model to other customers, whom want to see it without any desktop software.
I find such exmaple:
http://realitymodels.northeurope.cloudapp.azure.com/rm/Krustpils_pils_3dtiles/App_CCWebViewer2/index.html
Is this somehow related to the ContextCapture web viwer?
If you have the 3mx file all you need is a web server (static) or a blob repository to publish the information.
Deploy on the internet (bentley.com)
I used this tutorial and worked really good
Host a static website in Azure Storage | Microsoft Docs
there is no simple online viewer where I can upload a model and share access, am I right?
If you are not a large scale business then no. You will need to have you own server and storage.