The OP asked:
Anyone have any thoughts on (hopefully not experiences)
whether putting a loop of, e.g. 1 foot in diameter, on a coax
run from an outdoor receive-only antenna

One turn of coax is all but not a choke. Then the loop is not
located after a better path to earth. It is just a coax loop 1 foot
diameter that will somehow stop lightning - without some other path for
lightning to seek earth. Somehow it will block lightning and while not
impeding radio reception. How many henries stops - not diverts - stops
lightning?

Richard Harrison has previously described this choke as part of a
system where lightning also has a conductive path to earth. Only with
earthing is lightning further discouraged - diverted - by a choke.

Choke can only discourage lightning when lightning has a
significantly more conductive path to earth elsewhere. A 1 foot
diameter loop of coax does not even begin to accomplish what that choke
would, nor is it defined as part of a system that includes earthing.
Just some of maybe five reasons why that single coax loop does nothing
useful.

A coax loop is really not a choke. A choke by itself does not even
stop what three miles of sky could not. But a choke can be part of a
system that diverts lightning to some other earthing path. Without
earth ground, even a choke would not be very effective. And a one loop
of coax does not even perform as a choke would. So many reasons why
that coax loops does nothing effective.

Then the numbers. How many henries does a single 1 foot loop of coax
cable create? Ballpark - maybe 1 microhenry. How does a microhenry
stop or block lightning? Would inductance existing in an uncoiled coax
wire actually do more to stop lightning? A significant difference
exists between stopping and diverting.

Richard Harrison wrote:
w_tom wrote:
"Do you think the loop will stop what three miles of sky could not?"

Depends on what kind of loops and how many.

I`ve worked in several broadcast stations that often got struck by
lightning. Their towers were the tallest things around. None of these
stations got significant damage from lightning. In addition, none of the
station equipment powered from the mains or appliances plugged into the
mains at the station ever was damaged.

All these stations used tower lighting chokes, one coil for each tower
lighting wire including the neutral going up the tower. Three wires,
beacon, side lights, and neutral were usually accommodated with tower
lighting chokes. Their primary function is to avoid sapping any of the
r-f energy from the tower. Another benefit is that the chokes reject
lightning too. They are substantial and all turns are wound side by side
(trifiler?) around a large ceramic coil form. The wire is large enough
to easily handle the load current. I never worked at a station that used
Austin tower lighting transformers instead of chokes, but I`ve seen
enough of them to suppose they must isolate about as well as chokes do.
One station I worked in had an FM antenna atop one if its AM broadcast
towers. Its FM coax was coiled at ground level to isolate the AM r-f and
it rejected lightning too. So, if you have enough of the right turns the
choke does effectively reject lightning. Inductance is proportional to
the size of the coil.

Best regards, Richard Harrison, KB5WZI