What is the transparencyd daemon for? transparencyd seems to be there since macOS Catalina.
I cannot find any information about it other than what the MAN pages say :
&quot;transparencyd is a system daemon that verifies transparency information 
for requesting clients. It is not intended to be invoked directly&quot; 

It occasionally tries to connect to server kt-prod.apple.com (17.56.48.13) via TCP/443
and some files in ~/Library/Application Support/com.apple.transparencyd:

What is the transparencyd daemon for?
It handles the API and SDK calls for developers to check user tracking entitlements and transparently request access to private data and set these preferences on a per-app and per-device basis.

https://developer.apple.com/documentation/apptrackingtransparency

Since 2010, Apple publicly has maintained that all privacy and tracking should be after we consent to what / how and when out data is accessed.

https://daringfireball.net/linked/2020/12/18/steve-jobs-on-privacy

There’s a lot of public angst now that the code has shipped and is being enforced - not everyone is a fan of informed consent and opting in to tracking or “transparency”.

https://daringfireball.net/linked/2020/12/18/swisher-facebook-apple
https://www.eff.org/deeplinks/2020/12/facebooks-laughable-campaign-against-apple-really-against-users-and-small

But to address your question, it’s the mechanism by which an application receives access to photos, contacts, files and other things by requesting that access from the operating system.