cannot install via composer

Branch 2.x of this module uses the PHP SDK for HubSpot APIs v3. The HubSpot API module still uses the legacy APIs, see ✨ Switch to PHP HubSpot API v3 SDK Client Needs review . There is ongoing work on this but it has not been merged yet.

Therefore you need to use a branch of HubSpot API. Please the following to your application's composer file, as found here. This should solve the issue.

"repositories": {
    "hubspot_api": {
        "type": "vcs",
        "url": "https://git.drupalcode.org/issue/hubspot_api-3334746.git"
    }
},

Please note that currently the module will not synchronize anything out-of-the-box. It will need some setup that requires development effort depending on your skillset.

Closing, please reopen if you need more support on installing the module via composer.