I'm straight male, Wife and I had several years of great marriage, sexually satisfying for both (she was a bisexual), no kids,  we love each other. All what I explain below happened over 18 months, very slowly with open communication between us. And we are going through this together.
After several years of marriage we were open to spice things up with a threesome. We did not have much luck finding females to join us for over a year. Wife started to enjoy sex with me less and less over the time too.  We decided to open the marriage - to allow for sex/relationship with other women only. We tried some new things in bed as well so that she would enjoy sex with me but it did not help - Wife doesn't enjoy it and I won't force her.
Lately she had her first few lesbian experiences after a decade - and she liked it a lot. Her and I now both know that her sexuality shifted to homosexual only. (I read about it and there are several cases about this fluid sexuality).
Well, here is where I need help. I love her a lot, she is my soulmate,  "the one". She loves me greatly, she cares about my well-being, she didn't cheat or anything, kept all the boundaries we set and it is hard for us both to go through this.

This is my biggest issue: We are now in an "open marriage" however we don't have sex with one another. I think I would be cool to continue with the open marriage concept if we still made love and had some other partners/flings on the side. But now I miss the connection/intimacy and I cannot saturate the need with meaningless sex with other women. When I think about it - ever since we stopped having sex in our marriage - I stopped enjoying sex with women outside our marriage... It actually makes sense.

I am not happy with how things are now. And I feel that staying in a marriage with a lesbian you can't have satisfying sexual relationship is not right for me, I feel like we became each others super best friends - as something is missing in the marriage (lovemaking/intimacy/special connection?) and over the last weeks I am depressed due to the concern that my wife and I will slowly replace each other with someone new due to the above. I expressed this feelings to my wife and we are taking some time to think on this.

Our marriage was great and now this. I know it is my/our decision if we should stay together or not but I would be grateful for any insights or advise you can provide. What should we do? What should we try?