Can't paste photos Thunderbird, M365 nor Yahoo webmail

Perhaps if you walk us through what you are doing someone can guess as to what he issue is, but if it affects webmail as well as mail clients it is probably third party software like an antivirus, or it could be your images. I know Apple images do not go well in emails as they use an Apple proprietary file format by default that blurs image and movie into a single file. These tend to appear in emails as a blank placeholder, often in a frame.