to begin mowing the yard on a Sunday morning in a residential neighborhood?

Nope did mine at 7 am. To hot to wait later.

No not in the heat of the summer.

go for it, be sure to have a 6 pack with ya in sight and one in hand.

they will leave you alone, for a while anyway.

I say no earlier than 8am. Mow away!

I like hops approach.

I say no; and if your mower is old school Charlie Brown push blade or a quiet electric mower, I’d say no time restrictions.
My across the street neighbor on the HOA board, however, disagrees
Her and the Karen gestapo say 10am.

Not a bit.

which time zone?

9am is the earliest for me, and that’s exactly what I’m gonna do

Picking they pay a service that normally makes at least twice as much noise with multiple equipment running at the same time. I generally do mine in the afternoon/evening anyway when less humidity but have zero issues with someone mowing early AM.

Ding, ding, ding
The Karens will group together and outsource landscaping duties to the same service.

Don’t even get me started on their reaction when I briefly park my boat in my semicircular front drive and work on it for a couple of days.

8am should be fine unless you live in a neighborhood with a HOA.
Living in the country most of my life, I never had to deal with those issues.

Mow away!

I usually start at 9:00 but have no problem with neighbors or lawn crews starting earlier.