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?
You could create a wordpress website and add a subdomain in the publichtml, then upload the scene folder to the server using filezilla or something. The problem is that anyone can download the whole scene and some shared hosts often block such access. I had this solution a while ago, but now I prefer Azure, it's really cheap.
Have you tried iTwins?
is it posible convert 3sm or 3mx to iTwin-model?
Yes. No conversion needed. Both 3sm or 3mx should both work natively within iTwins.
I have not tried it myself just yet but have seen it done many times.
Only issue the link is not public and need login.