One thing I’d add is don’t just look at rankings, check what type of Yahoo traffic dropped. Sometimes it’s not classic search, it’s browser/startpage/syndicated stuff and the pages that vanish are different than Bing organic.
For actual Yahoo/Bing SERPs, I’ve seen boring stuff work better than fancy SEO lately... exact intent title tags, old pages refreshed properly, tighter internal links from pages already indexed, and getting the URL re-crawled fast. Bing Webmaster Tools + IndexNow is basic but a lot of sites still don’t have it setup right.
Also schema seems to help more there than people give credit for, especially FAQ/product/local type pages. Not magic, but if competitors are sloppy it can push CTR a bit.