This is an intersting thread. I've been doing SEO 17+ years. Since Bing was such a small share of search traffic I never did any optimization specific to Bing and in most cases if I ranked well on Google I also ranked well on Bing for a variety of client websites. I never set up rank tracking on an ongoing basis for Bing just spot checked a couple times a year out of curiosity.
I have one client though that is top 4 for most target keywords which include a couple city names so they are georgraphic specific. They are always in the 3-pack on Google and like I said, top 4 organic. These are middle-level competitive keywords. Not obscure but not like 'car insurance'. On Bing they are in their 3/4 pack almost as often as Google but the organic ranks are like night and day. They a BURIED as far as organic rank on Bing for most target keywords right now. Granted I stopped even spot checking their Bing rank 4+ years ago since it represented less than 10% of their traffic even when they ranked high. So something in the last 5'ish years or so definitely changed with their algo and we didn't do any sort of grey/blackhat stuff for this website EVER.
As others have eluded because of Bing Chat (now CoPilot) and Edge now running on Chromium and is more memory efficient the Chrome, many are using Edge + Bing. I use Edge now but still use Google Search as I know Bing is AT BEST *almost* as good and never going to be BETTER than Google so why even bother using anything other than Google.
Edge just hit an all-time high for browser share of 13% which is still small but it means it's a bigger player now and of course it defaults to Bing.
So I started to get concerned we were leaving money on the table ignoring Bing and this client's service area happens to be Greatter Seattle including Redmond/Bellevue where Microsoft is headquartered so they get a higher than average proportion of Bing users in their market.
But still, I just checked the stats and USA only Bing is 7.8% as of late with only a very small increase in recent months. If you are outside the USA it's less than half that so I wouldn't even think about Bing at all if you are targeting users outside the USA.
https://gs.statcounter.com/search-engine-market-share/all/united-states-of-america
I would guess at best in this client's market it's 50% higher than nationwide so 15% at most. That's significant but to me it's still not enough to warrant me spending a lot of time trying to optimize for Bing. One reason there's less information on Bing algo factors is for the history of SEO far more experimentation was done for Google so there's just a fraction of the knowledgebase for Bing. That's why no one has a clue. And now with Google's release of Gemini Pro 1.5 of Feb 15 2024 (replacement for Bard), Google has essentially caught up on AI (as I expected they would) so their modest gain in browser and search share may have plateaued at this point.
So in a nutshell, obviously you want to at least be indexed, but from everything I read in this thread the only time you might want to spend regarding Bing optimization is look at their Webmaster tools reports and tweak your content a bit based on semantic keyword suggestions. If anyone else has any other suggestions of things that have high potential return for time investment with Bing, I'd love to hear them.