Felt the need to also jump in on this thread, because the fact it's this much of a struggle to sort out an email signature is unreal, made new branded email signatures for the company I design for in the old Outlook that worked with no issue.
For those that use new Outlook it seems that no matter what I do nothing works, copy + paste doesn't work unless it's from Outlook -> Outlook (then of course you have the formatting issues, impossible to work around if you're designing signatures for 20+ people), drag and drop is only a temporary fix, after a while it seems that the images you place just phase out of existence and you're left with alt text.
Image below is taken from the same email thread not even 30 minutes apart, I initially thought this was an issue due to the email thread length, compressing the images to alt text so it loads quicker, but others have experienced the exact same thing sending one to one emails where images in the email signature suddenly disappear.
This also in turn seems to impact the actual saved signature itself, so the images remain missing in new emails.
https://learn-attachment.microsoft.com/api/attachments/334551de-2d3c-4ab8-9c20-168eb3f7950d?platform=QnA&fud_access=wJJIheezUklbAN2ppeDns8cDNpYs3nCYjgitr%2BfFBh2dqlqMuW7np3F6Utp%2FKMltnRRYFtVjOMO5tpbpW9UyRAwvLeec5emAPixgq9ta07Dgnp2aq5eJbnfd%2FU3qhn54q2bg8c4TjeoFR9DL5%2BljRYoREqvHlca9fqCv5EiwoucW%2B1JxJlj1qKefuM73pK1JFwXFmaN51kScIQbU3eR9pmbyMAj0IR%2F2VGBddE5z3Oo6Wi3tx3HUx%2BRdi%2BSerWx8DaQHAUy0eeD%2BKTztus1OLq%2FPP8hX2YJvzzyzTBGW5qfNFIEuReYwr3s%2B%2BtQQdz7EwxRmjFZOTFbbUmRrpq1wGHGO%2F8OCsDD8BQCloAX9OoSowK2hUkFvGlE60QVODckIVVFgicW8pCnIios8wQXAt%2BzNc27%2Bi7AKEAyKJmsHPAk%3Dhttps://learn-attachment.microsoft.com/api/attachments/7f7812f2-d3ce-4bd9-80e4-3fd3ef37db01?platform=QnA
