We know there's plenty of Teams resources and help guides. But often an organisation will make their own guides that reflect the context of their organisation. It may include the "why" Teams to your particular organisation, governance, case studies of some project/teams using it successfully, and so on.
Where does an organisation make these Teams resources available
on their Intranet would be the most obvious place
But I also think in the Teams help page within the Teams app would also be a good place
pity you can't bake in your organisation's Teams resources into this page
I'd also include a link to ask a question to the Teams support group
There sre options like creating a training portal or making your own content on SharePoint or any other platform and tab it into all teams! Also there are support bots to add and also ability to create own bots and tabs and use app policy’s to tab it in left navigation!
But of course it would be nice just to edit and customize the existing one