Overcoming Unity IL2CPP compiler issues ("error: unknown type name")

Question

I'll try to be brief...

Unity 20022.3.4f1, building for Android w/ IL2CPP backend and ARM64 (for Pico VR).

imported DLL's (through nugetforunity)

1. Accord.3.8.0
2. Accord.MachineLearning.3.8.0
3. Accord.Math.3.8.0
4. Accord.Statistics.3.8.0

We are trying to build our Android project with the above DLL's, and are constantly stumped by the IL2CPP compiler with the following error:

[Bee] failed with output:
PROJECT\Library\Bee\artifacts\Android\il2cppOutpu\cpp\GenericMethods__21.cpp(10621,91): error: unknown type name 'Sparse_1_t2B37F496308C51B005F6B737F6DA2974891E4668'
typedef double ( *func_L_28) SquareEuclidean_t7D455591968D62E424E96927FD8DDA6231CC1501*,Sparse_1_t2B37F496308C51B005F6B737F6DA2974891E4668*,Sparse_1_t2B37F496308C51B005F6B737F6DA2974891E4668*,const RuntimeMethod*);
                                                                                                        ^

I have included a link.xml file next to the imported DLL folders (Assets\Packages\link.xml) which has the following contents:

<linker>
    <assembly fullname="Accord.3.8.0"/>
    <assembly fullname="Accord.Math.3.8.0"/>
    <assembly fullname="Accord.Math.Core.3.8.0"/>
    <assembly fullname="Accord.MachineLearning.3.8.0"/>
    <assembly fullname="Accord.Statistics.3.8.0"/>
</linker>

I've tried changing the stripping levels, changing the link.xml to include "preserve="all" for each of the DLL's... and I'm just not getting anywhere.

Does anyone have any idea why IL2CPP is tripping up on these DLL's?

I know that the IL2CPP compiler is finnicky, but it is necessary for us to be able to use TOBII Eye Tracking with the Pico Neo 3 eye.

As always, any and all help would be greatly appreciate.

Mike