Dev Hub is available in your production org or in Developer Edition orgs (with much lower limits). It is not available in sandboxes of any edition.
does it mean it's need to provide production access to every developer who needs to create a new scratch org?
Yes, but you can configure them with minimal permissions to interact only with the SFDX objects. ...
This is quite a large topic, so I might not be able to do it justice in just a single StackOverflow answer.
The position you should try to get to is that the source control repository is the source of truth, and when you get there then specific environments become less important.
The tactical answer to your question is that Visual Studio Code with the ...
Could you try this configuration file (borrowed from answer in this post with updates on settings) :
"orgName": "Your Org Name",
"Communities", "PartnerCommunity", "ForceComPlatform"