We're MUCH more out as swingers than poly BUT we're new to poly plus covid has meant we haven't seen many of our closest long-time friends since we began the poly journey.
Regarding coming out as having an open relationship - we have a strong circle of friends from when we were all in our early 20's. It's amazing really how close and large this circle is. We are the longest relationship in there but followed by a few other couples...
We had some years where it was really apparent we were unhappy together, going through the motions. Opening up came with growing pains but it brought us back together and back to being in love not just in life together.
So we decided it was right for us to tell our closest friends why we were suddenly so fucking good together. And being a circle like that it was common knowledge pretty quickly because the ladies love a gossip. No big deal - just a few knowing looks and a little degree of awkwardness for me from frustrated husbands until they all worked out really we were the same people.
This was about 18 months into our journey. Since then my partner leaving a swinging app open on the ipad meant 2 of our then teenage kids know, plus my mum (dad when alive) and sisters. The kids took a while to settle but apart from 1 sister my family were terrific - my dad saying we seemed happy and whatever made us happy was fine by him. My relationship with our now adult son has never fully repaired, he went into slutshaming and seeing his dad as a victim but he now lives with us so it's not broken just never the same since. That's the only real negative. Last year our daughter gave me her blessing to just be us however we want. Took her moving to one of the world's biggest cities to gain that maturity.
I then made my partner tell his dad because I thought it seemed fair. This is all 2015 - his dad bless him said 'Do I need to do anything?'

Partner said no and he was relieved and no issue at all.
Then we have told a few different close friends over the years not many - it's not their business.
So when I caught feelings and poly came up I had to tell a few friends in the swinging community that felt huge but really it's new and covid has messed up plans so I have told my closest vanilla girlfriend, another vanilla male friend and that's it. My partner has probably told his best friend no secrets there.
It was my partner's 50th a few months back and I was hoping we'd invite some of that old friend circle, a few new friends and my boyfriend and I would have the opportunity to break the news in a friendly, low-key matter of fact fashion but we had lockdowns so that never happened.
Because of physical distance and a few hardships I'm back to not feeling as deeply entrenched with the new boyfriend as I used to so any urgency has lifted - we're in FWB who care deeply territory until life let's us feel romance again. I hope it does and I am looking forward to telling a good vanilla friend about him next week when I see her.
So we've come out (with ENM) happily, like a bandaid on a sore wound AND slowly but surely. And not at all to people where it's just not their business. My partner and I both want to be really open - especially about poly. We feel we have an obligation to all those who come after us - like gay people did in the 80s and 90s (but without the stigma of AIDS).
I don't know how our poly journey will continue, we may slip back into just ENM without the feels if there's no-one special for either of us - but we want others to understand that they can tread off the path of relationship expectations.
My boyfriend seems to be mono - although he has been/could be sexually open he just chooses not to. He does not want anyone - primarily his family - to know, but he's proudly told a few old guy friends - and that's part of why I think our relationship might not to go the distance. He's traditional and worried about what others think. He might be able to sit in the lovezone and keep moving with us but for now being judged for being different seems to terrify him as a concept. But he also opened up to me and said he doesn't like the idea people might see him as gay (he's not) - so that's entrenched social conditioning that is so not for this era... I probably need to put a disclaimer that he's not a judgy guy, very gentle soul, doesn't look down on others ever himself - maybe got teased as a kid who knows.