Microsoft wrote their own replacement and it's better-integrated into Office than the old editor was. Search for "insert equation" in the Office search box. The new one supports both the old editor's style of input and actual LaTeX inputs. Heed the dates on articles talking about it: TFA is from 2018 before they wrote the new editor.
You can then download the image. The only thing I think they should add is the equation string as a comment to the images so you can upload and continue editing without a proprietary file format.