Trying to find a podcast (ep?) focusing on "inheriting a new infra"

You might find want to check out the SysAdmin Today podcast. The host runs through lots of stories of issues faced on different subjects. https://sysadmintoday.com/

There is even a recent episode about taking over a network that may be useful: https://sysadmintoday.com/sysadmin-today-60-taking-over-a-network/

And another about on boarding a new network from an MSP perspective. https://sysadmintoday.com/sysadmin-today-32-onboarding-new-network/

Is there a particular podcast you were thinking about?

That's fairly vague considering there are hundreds of hours of this topic being discussed.