Tools and settings that filter and block explicit or inappropriate content from search results.
I'm still waiting to hear back on the "enable Bing Chat AI while strict SafeSearch is enabled" bit, but I believe I found the setting that used to be in "Services & Add-ins"
If you go into the M365 admin center (You may need to click "Show All..." to reveal all navigation options) - then in "Settings" go to "Search and Intelligence", then go to the "Configurations" tab, and there should be a card for "Microsoft Search in Bing for Work and School". The wording around the setting makes it sound like this may only appear if you have both an "education" and an "enterprise" service plan. Choose "School" and you'll be locked to Strict safesearch, or "Work" and you'll be locked to Moderate safesearch.
(Accurate as at Aug 2023)