For the OAuth flow a client id is indeed required, the OAuth docs from steam says the following:
Steam’s implementation is based upon OAuth 2.0.
During your initial setup you will need to contact Valve with the following information:
What permissions you need the user to obtain. The required permissions are listed below with each API call.
The token lifetime.
The redirect URI to send the user back to after completing authentication/authorization.
In return, Valve will assign a Client ID for your implementation.
The API Key can be used to access parts of the webapi that are not public, you can add the key to the querystring to access these endpoints.
To let a user login with steam you will probably need the OpenID instead of OAuth2 and it looks like the docs are not correct or outdated. I’ve checked the passport-steam module and they use OpenID 2.0 for authentication. OpenId 2.0 is not the same as OpenId Connect and not compatible with OAuth2. It looks like you will need a custom extension to get Steam login with Wappler.