How to reproduce:
1. Open the user's attached project "New Unity Project.zip"
2. Open "TestMatChanger.cs" in "Rider EAP9" for Apple Silicon
3. Add a breakpoint in "TestMatChanger.cs" on line 25
4. Enter Play Mode in Unity
5. Attach debugger to Unity in Rider
6. Press the "mat1" button in the Game window of Unity Editor
7. Exit Play Mode using the play button in Rider

Reproducible with: 2021.2.0a19, 2021.2.0b5, 2022.2.0a4
Not reproducible with: 2019.4.29f1, 2020.3.15f2, 2021.1.16f1, 2021.2.0a18

First lines of the stack traces:
Thread 77 Crashed:: Debugger agent
0 libsystem_kernel.dylib 0x00000001876ece78 __pthread_kill + 8
1 libsystem_pthread.dylib 0x000000018771eb98 pthread_kill + 292
2 libsystem_c.dylib 0x00000001876674e0 __abort + 116
3 libsystem_c.dylib 0x000000018766746c abort + 116
4 libmonobdwgc-2.0.dylib 0x000000013515c2e8 monoeg_assert_abort + 32
5 libmonobdwgc-2.0.dylib 0x0000000135141700 mono_log_write_logfile + 312
6 libmonobdwgc-2.0.dylib 0x000000013515c500 monoeg_g_logv_nofree + 172
7 libmonobdwgc-2.0.dylib 0x000000013515c5bc monoeg_assertion_message + 40
8 libmonobdwgc-2.0.dylib 0x000000013515c600 mono_assertion_message + 32
9 libmonobdwgc-2.0.dylib 0x0000000135136a18 deregister_root + 64
10 libmonobdwgc-2.0.dylib 0x0000000135176894 GC_call_with_alloc_lock + 72

Notes:
- Not reproducible on Windows
- Not reproducible with Visual Studio 2019