Albert,
Can someone help me
sort out how our members can read the list messages on the web and
respond from there? So far it seems one must use a mail client in
order to be able to respond to the messages.
What J said.
Also, each email from your group has some links. Here is an
example of an individual email, with the links at the bottom (the
links will be formatted differently if the message from your group
is plain text, rather than formatted):

View/Reply Online brings you to that very message. Group
Home brings you to the group's Home page. Your members can
use either link to find your group's pages, and from there the
Messages list.
Note: if the Privacy section of Settings page of your group has
Visibility set to one of the private (not public) archive choices,
then your members will have to log in to Groups.io in order to
access the Messages. In the upper right of a Groups.io page they
should see the Log In link:

As members of your group they already have an account, so they
don't need to use the Sign Up form. They may not have a password
for their account yet, and if that's the case the Log In form will
give them a couple of alternatives:

Either highlighted link will send them an email message that will
let them log in to the site. The don't have one yet?
message will have a link that will bring them to their account
page, where they can set/change their password. The Email me a
link to log in message will have a link that brings
them back to the page they started at.
Once logged in to the site they should be able to see its Messages
page:

Members won't see the Admin button on the left, but they
can use the buttons in the left column to view various pages
within your group.
Shal
--
Help:
https://groups.io/static/helpMore Help:
https://groups.io/g/GroupManagersForum/wikiEven More Help: Search button at the top of Messages list