async-get stalls during init on certain platforms

[PythonNut]

Under certain conditions, process sentinels don't run during init. Because of this, if one does async-get (or similar) during init, the init will stall indefinitely.

I have reproduced this using the emacs (version 27.1-3) package from the Arch Linux repos running in graphical mode (Gtk). (And also the AUR package emacs27-git). There is also a report of this happening on a more recent version of macs in the above S/O link.

I realize this may be annoying to track down and might not even be fixable, but I am willing to provide any assistance I can towards solving this.