Do you have a Yahoo account?

I do not, and am only able to access attachments from the link in the
original message, not from the other messages in the thread (where it
says "Check out the automatic photo album with 1 photo(s) from this
topic.").

EG. in the thread "Sea cock & thru hulls", (S)Miles Bernard attaches
an image in his message sent 6 Nov 2017 20:15 PST - there are two
attachment links in that, only one of them works for me, the other
shows me a Yahoo login (and I have no Yahoo account).

I can also see the attachment sent by Heinz Stutenbäumer at 9 Nov 2017
09:57 in the thread "phased electronics replacement" - that is
actually in the body of the message, and I don't even have to click a
link, Much better!

I think maybe one of these posters posts via email, the other via Yahoo Groups.

I would much prefer a plain text mailing list.

Andy.