[Finding groups and the "closed membership" barrier]

Rather than searching for groups, perhaps you should search for the events or the sims where the members of those groups hang out.  Whether this makes sense, of course, depends on what your interests are, the sort of folks you're looking to meet up with and the sort of things you're looking to do.  In any case, the destination guide and the events list seem like they'd be a better starting place than groups.

As for the reason for the "closed membership" barrier, at least in some (many?) cases, there's a good reason for that.  Panhandlers who join open groups for no purpose other than to spam them for "loans".  Very annoying. 

[SSL handshake failed ....?]

Best answer I can offer is the Phoenix viewer.  That's my fav anyway.

[Can anyone advise me on embedding scripts in an object?]

You don't really need to make a prim, if you right click on any modifiable item and choose Edit from the pie menu, you'll be able to access the contents tab, then drag the script from your inventory to there.

[To me, I'm clothed. To the REST of SL, I'm bucknaked.]

This happened to a guest at one of my live music events recently.  This was a semi-regular attendee, so I know she was telling the truth when she said she was fully clothed in her view.

This was not a problem with her video driver, she WAS seeing the clothing, the other guests were not.  If it were her video driver, that should have been the other way around.

This was not a problem with the clothing being high resolution.  That would have caused her to show as all grey.  Her skin, in all it's detail, was showing.  Her clothes were not.

Fortunately, I saw her, let her know, she ran inside the building (where there was no one) and relogged.  When she came back out, she was clothed just fine.  As I said above, I know this lady, this was no fake.

This also happened to one of the musicians at one of my shows.  He finished his set, tp'd off the stage and was suddenly naked.  He had been fully and properly clothed thoughout his performance, the nakedness happened when he tp'd the short distance from our stage to the bridge over looking the stage (our dance area).  He immediately tp'd home, relogged and then had clothing on.

I suggested to both to raise either an AR or a Jira as this is surely either a griefing (which I don't think) or a bug (which I strongly suspect).  My advice to anyone who experiences this, first duck for cover, relog and then raise a ticket.

Unless of course, you're at a nudist resort . . .