How can I connect Libre 3 app with Apple Health? It’s the only way I can connect with an InPen. This is very important for diabetics and their care!

We’re not Apple. We’re other users like you, and some are third-party developers.

There is no means to connect an app—one that you don’t control the app source code—with Health app or other such.

You can request the connection be added by the app developers.

I have tried a few apps those can read data from LibreConnect and copy data into Apple Health app.

1) Gluroo / Nightguard

2) GlucoseDirect (beta)

I was able to read Libre3 data using those apps and write into Apple Health.

And those specific applications were designed to read Libre3 data and share their data with Apple Health. That does not mean that Libre 3 has been designed to do that. Talk to the developers of Libre 3.