Issue with "three loading dots" showing on Oculus when launching new Activity from Android plugin

Hi!
I have task to launch a native Android app (specially edited) on the Oculus Quest 2.
I am doing minimal research on this matter, created a primitive native Android Kotlin plugin and launched it just on the Oculus using Unity. Everything works fine. Activity started and I can interact with Android UI.

But when I build project for Oculus (with XR plugin and etc), I got "three loading dots" and nothing else (log shows that the activity has gone through all the stages of it's life cycle).
As an experiment, I tried to call a function from my Android Native Plugin, which should display a regular Android Toast, but it also doesn't work out (doesn't appear). But if call a simple function implemented in the plugin (e.x. multiplication function), then the logs contain the result of its execution. That is, the plugin is connected and working.
I have a lot of experience in writing native apps, but I've been dealing with Unity+Oculus for about a week and don't know where the problem might be.
Maybe I can't run the Android UI (Activity, Toast, etc) from the .aar plugin on the Oculus? =(