Hangups on MacOS, Unity 2020.3.22f1 LTS, editor memory leak?

I am experiencing Unity (edit: 2020.3.22f1) becoming unresponsive at various moments during its use but quite frequently, on macOS Catalina 10.15.7.

The editor will beachball when hitting save, when I try to enter play mode or when switching from Rider to Unity. The project is stored locally and not being synced with services such as Dropbox nor git. The Activity Monitor shows Unity as "not responding" and I can use Force Quit to end the program. It doesn't use exhorbitant amounts of CPU % and 0 % GPU when it has crashed.

It does, however, show up in the memory overview twice (see screenshot). Same goes for the Network overview in activity monitor.

There seem to be no kernel panics (the OS is fine, Rider is fine, only Unity is unresponsive).

Also: 1 TB harddrive with plenty space left (300 Gb).

The project also uses Metal (it is enabled in the project settings and <Metal> is shown at the top of the program).

The Editor.log does throw a lot of these lines:
Fallback handler could not load library /Applications/Unity/Hub/Editor/2020.3.21f1/Unity.app/Contents/Frameworks/Mono/lib/(filename, mostly .dlls)
Could it be I am missing a dependency?

Other than that I have not been able to figure out what the exact culprit is and googling has so far not helped. I am out of ideas.

Machine specs:
macOS Catalina 10.15.7
Mac Pro (late 2013)
3 GHz 8-Core Intel Xeon E5
64 GB 1866 MHz DDR3 memory
2x AMD FirePro D500 3GB

Activity monitor, memory:

Activity monitor, network:

 

I installed a newer version of the editor but the same behavior happened. I also noticed there's an editor-prev.log? This was also created today. At the bottom it seems to mention a memoryleak. This log was produced by editor version 2020.3.21f1 before I decided to try 2020.3.22f1. At the end it says;


Fallback handler could not load library /Applications/Unity/Hub/Editor/2020.3.21f1/Unity.app/Contents/Frameworks/Mono/lib/libKernel32
Fallback handler could not load library /Applications/Unity/Hub/Editor/2020.3.21f1/Unity.app/Contents/Frameworks/Mono/lib/libKernel32.dylib
Fallback handler could not load library /Applications/Unity/Hub/Editor/2020.3.21f1/Unity.app/Contents/Frameworks/Mono/lib/libKernel32.so
Fallback handler could not load library /Applications/Unity/Hub/Editor/2020.3.21f1/Unity.app/Contents/Frameworks/Mono/lib/libKernel32.bundle
Fallback handler could not load library /Applications/Unity/Hub/Editor/2020.3.21f1/Unity.app/Contents/Frameworks/Mono/lib/Kernel32
Fallback handler could not load library /Applications/Unity/Hub/Editor/2020.3.21f1/Unity.app/Contents/Frameworks/Mono/lib/libKernel32
Fallback handler could not load library /Applications/Unity/Hub/Editor/2020.3.21f1/Unity.app/Contents/Frameworks/Mono/lib/libKernel32.dylib
Fallback handler could not load library /Applications/Unity/Hub/Editor/2020.3.21f1/Unity.app/Contents/Frameworks/Mono/lib/libKernel32.so
Fallback handler could not load library /Applications/Unity/Hub/Editor/2020.3.21f1/Unity.app/Contents/Frameworks/Mono/lib/libKernel32.bundle
Fallback handler could not load library /Applications/Unity/Hub/Editor/2020.3.21f1/Unity.app/Contents/Frameworks/Mono/lib/libKernel32
debugger-agent: Unable to listen on 96
[Package Manager] Server::Kill -- Server was shutdown
Checking for leaked weakptr:
Found no leaked weakptrs.
##utp:{"type":"MemoryLeaks","version":2,"phase":"Immediate","time":1636280164133,"processId":9418,"allocatedMemory":177826,"memoryLabels":[{"Default":878},{"Permanent":384},{"Thread":567},{"Manager":5256},{"Geometry":-672},{"Texture":144},{"Shader":408},{"GfxDevice":7488},{"GfxThread":3456},{"FontEngine":4096},{"Physics":1},{"Serialization":1016},{"File":8454},{"String":34520},{"DynamicArray":29839},{"HashMap":22343},{"UTF16String":426},{"Utility":400},{"Curl":1056},{"PoolAlloc":120},{"GI":336},{"VR":1696},{"NativeArray":744},{"Secure":15998},{"Subsystems":96},{"EditorGui":1728},{"EditorUtility":2368},{"AssetDatabase":7425},{"RestService":72},{"UnityConnect":26388},{"Collab":795}]}

 

Opening the project on my Windows machine with the same version of Unity results in that Hold on... progress bar appearing. Same results.

See this topic: https://forum.unity.com/threads/editor-progress-bar-stalls-request-for-bug-reports.1137817/