Connect in what way? On S1? Group them: yes. 

To have surrounded sound 

I think I have read that the play 5 gen 1 won’t work on the playbar. To give surround sound 

You are partially correct: it’s the Gen 1 Play:5’s that can’t be used as surrounds to any home theatre device. 

Can any other Sonos speaker work 

Source please?

Just about any other Sonos speaker can act as a surround speaker to the Playbar.  If you are on S1 then speakers that can connect only to S2 are ruled out. That still leaves you the Play:1, Play:3, Play:5 gen 2 and Sonos One. Oh and at least some Symfonisk speakers. 

The issue with the Play:5 gen 1 is that it lacka the 5GHz capability needed for Sonos HT surround sound.

Sorry - been out all day so not monitoring the forums. Surrounds info here https://support.sonos.com/en-us/article/surround-sound-guidelines-and-limitations 

Ahah, was not aware of that, makes sense though. I do have some spare Gen 1 P5s but evidently never tried using them as surrunds.

It’s also why the CONNECT:AMP requires wiring for surround duty. No 5Ghz for it, either!

So if one was to hardwire the Sonos Play 5 Gen 1 would they work? I understand not suppurting 5Ghz but would not need it hard wired

No, the Play:5 (Gen1) can’t be used as surrounds. Hardwiring does not change that fact.