[mac] unity unusable; hangs indefinitely importing assets/compiling scripts

i have a yearlong project running unity `2021.5.15f1` on mac. in the past week, unity has been completely unusable -- it hangs indefinitely every time i use it. it exhibits two problems:

1) when loading the project, the editor hangs indefinitely during "Importing...". i can bypass this by deleting the project-local `Library` folder, and re-importing everything. after that, the project usually opens once.

2) however, after a couple rounds of (sometimes one round) of changing scripts, the editor will hang indefinitely recompiling scripts. force-quitting the editor (or killing the `dotnet` process and quitting the editor normally) and re-opening the project then reproduces problem 1.

the end result is the editor is completely unusable for me at the moment. it works fine on my collaborators machines (all windows). i've tried completely uninstalling unity/hub and purging unity's many cache/log folders scattered around the macos `Library` and `~/Library` folders and reinstalling, but it didn't solve the problem. i've tried upgrading everything to `2021.3.18f1`, the current 2021 lts version. in both cases, it seemed like it was alright for a few minutes before returning to the above described behavior.

attached editor/bee logs