"Blazor Polar Area Chart" do not catch ALFA settings in background in Android app

[MaMon1963]

Hi, I have a MAUI Blazor Hybrid App (.NET 8) that uses Blazor Bootstrap 3.1.0 charts.
In the "Blazor Polar Area Chart" that I implemented, I have two series of values ​​that are displayed with completely black background arcs.
In fact, it is not possible to apply the ALFA parameter in the background with the "ToRgbaString" function and the coloring is also lost.
Instead, if I use "ToRgbString" to determine the background color, they are displayed without transparency.
I tried with two different Andoid 14 terminals (a Samsung A53 SmarPhone and a C10 Tablet) the result does not change.
While on the Android emulator made available with Visual Studio 2022 the code works perfectly.
I observe the same behavior using the example code provided by the Demo Blazor Bootstrap site.
Has anyone encountered the same problem or can help me solve it?
Thanks in advance.

[MaMon1963]

I would point out that in other parts of the same application, such as the grid filters row, the opacity parameter works and I believe this is also based on RGBA.