#69756 has several failures that occur across Mono:

Assert.Equal(unchecked((nuint)0xFFFF_FFFF_FFFF_F800), NumberBaseHelper<nuint>.CreateChecked<double>(+18446744073709549568.0));

Assert.Equal(unchecked((nuint)0xFFFF_FF00_0000_0000), NumberBaseHelper<nuint>.CreateChecked<float>(+18446742974197923840.0f));

In both cases the double and float used is the smallest representable double that is less than ulong.MaxValue and therefore it should always succeed.

However, Mono incorrectly throws System.OverflowException instead. The same tests exist for ulong where things are passing as expected.