This PEP was mentioned on python-dev at least at https://email@example.com/message/WQ64ZGBE... and https://firstname.lastname@example.org/message/YVSOOFLC.... This was also covered by the PEP 596 discussion and https://email@example.com/message/Y4XFD7OW... as PEP 602 was split out of PEP 596 and stated as such in that discussion since the latter PEP did double-duty initially as the 3.9 release schedule and changing the release cadence.
I will also say that https://discuss.python.org/t/pep-602-annual-release-cycle-for-python/2296 received 84 replies from 22 participants and 83 replies from 13 people for PEP 605 at https://discuss.python.org/t/pep-605-a-rolling-feature-release-stream-for-cp... (the PEP 607 announcements never got replies anywhere from what I can tell) so there was participation by folks.
When it comes to PEPs, people seem to have naturally gravitated to announcing PEPs on the appropriate mailing list and then directing people to dicsuss.python.org for discussion (specifically the https://discuss.python.org/c/peps category which is open to the public). If you consider that making MLs obsolete then I guess that's seems to have happened at least when it comes to general PEP discussion.