As someone with no background in IT / CS, I am working on a project that requires me to get some understanding of the entire IT / systems landscape of a company - i.e. the various Hardware and Software requirements as well as the market leaders offering these products and services.  What report / webpage / any other resource would be a good starting point to understand this basket of markets?

Start with the "Stack" Mental Model, Then Dive into Reports

For a non-IT background, don't dive straight into product lists. First, build a mental model of the "IT Stack." Most landscapes break down into four layers:

- Infrastructure (Hardware/Cloud): Where things run (e.g., GCP, AWS, Azure, Data Centers).
- Data: Where information lives (e.g., Snowflake, Oracle, SQL, BigQuery).
- Applications: What the business uses (ERP like SAP/Oracle, CRM like Salesforce).
- Security: The wrapper around it all.

Best Starting Resources:

- Gartner Magic Quadrants & Critical Capabilities: perfect for seeing market leaders in any of the above categories at a glance.
- IDC MarketScape: Great for deeper dives into specific hardware/vendor assessments.
- G2 or Capterra: Good for quick, user-level reviews to balance the analyst view.

Start high-level with the Quadrants before getting lost in technical spec sheets.

Search for Microsoft tutorials if you're looking to get an understanding of the technology landscape. It helps to get hands on experience with the technologies and frameworks including Azure and AI, however, start small like understanding SQL and databases.

Once having found out all the systems your company uses (don't forget freeware too), you could list the main capabilities that your colleagues use them each for (you'll need help from your colleagues to confirm these). Try to relate each of these to generic, industry-standard abilities that you can choose to buy / develop services for. It will help you spot what is of most value to your organisation and where to focus resource.  Some unusual capabilities that your organisation does may need to be broken down into more generic components to be able to match to industry-standard - or a bespoke service may be required. 

I would start with accounts payable and ask for a list of invoices paid to IT hardware and software vendors to get an idea of what is currently in your company.

no single report can help and cover all, but I suggest to approach this from these angles: Data, AI/ML, Security (TRiSM) and platform/Infrastructure (including hardware).
Some Gartner reports can help at high level.