Describe the technical infrastructure (aka the underlying hardware) the system is running in. That shall include:

• nodes, i.e. processors, server, cluster… and their
• relations (channels), i.e. bus, network or wireless connections,
• additional hardware elements, i.e. firewall, router, switches, storage etc.

You could either use UML deployment diagrams or free-form graphics, like shown below:

(diagram by UML-diagrams.org)

In case your stakeholder like such graphical icons or symbols: use a consistent set of such symbols with a defined semantic!

Delegate hardware documentation

Try to delegate the hardware and infrastructure documentation to the appropriate stakeholders.