How to reproduce:
1. Open the user attached project (IL2CPP_Debug.zip)
2. Make sure the Editor's External Script Editor is set to Rider
3. In the project's Assets folder find and open the NewBehaviourScript
4. Add a breakpoint on the 16th line
5. In the Unity Editor make sure the Scripting backend is set to IL2CPP
6. Build the project with "Development build" and "Script Debugging" enabled
7. In Rider in the top right by the play button select the "Standalone Player" in the dropdown
8. Press the Debug button to run and debug the player
9. When the player loads focus on Rider and observe the breakpoint

Expected result: the breakpoint is triggered
Actual result: the breakpoint is not triggered

Reproducible with JetBrains Rider Editor: 3.0.14 (2019.4.38f1, 2020.3.34f1, 2021.3.2f1, 2022.1.0f1)
Couldn't test with: 2022.2.0a12 ("Unable to connect to Unity Executable" error when debugging player built with IL2CPP)

Reproducible on Ubuntu 20.04 and Windows 10

Note: The breakpoint is triggered when the player is built with Mono