FYI: I have added a code that works for me in that thread.

I have also filled a bug report with video that clearly shows there is something wrong: FB9216031

I'll try that, but I thought maybe there is any documentation regarding multithreading inside app and system extensions that I couldn't find?

Thanks! I'll try this. But what I found during testing of DispatchQueue.asyncAfter is that it works only while connected to wifi. As soon as I turn off wifi, looks like it stops getting called. Then when I'm back on wifi, it resumes.

Finally filled a bug report: FB9623293

Yes, both are NEPacketTunnelProvider subclasses. But sendProviderMessage is not suitable in our situation, because I have to communicate with it even before I want to start a connection . Regarding com.apple.security.temporary-exception.mach-lookup.global-name - app works perfectly wthout it. I still have added it just for tests and nothing changed. The problem arises on some machines all the time you open the app, and on other machines only after reboot. Looks like on Catalina we get this error after each computer restart, on Big Sur and Monterey you have to restart 2-3 times before you get Couldn’t communicate with a helper application on app start. We are doing this check on app start (applicationDidFinishLaunching), maybe that's too early?

Moved comment to separate message to have proper formatting

Thanks! This is really useful information that is not so easy to find! :) Can you please take a look at my message right above yours? This thing concerns me the most - I have some messages that are just not saved if called from within one more function. I tried setting Enable-Oversize-Messages to true, but that doesn't seem to help.

Update: full command to get logs:  sudo log collect --device-name "DeviceName" --output ~/Downloads --last 30m.

Second update: I tried setting Enable-Oversize-Messages to true, Presist and Enable both set to Debug to save everything that's possible, but that doesn't seem to help, when downloaded with a command from my last comment - logs made with log2 are gone.

Wow, so cool! Thanks a lot! :) In my case it was wrong case of path inside *.xcworkspace/contents.xcworkspacedata.