The image library accepts HEIC and HEIF photos, such as those taken on an iPhone, wherever images are uploaded: Your images, the image picker, Chat, Kanban cards, the native app and the API. A HEIC photo is converted to a JPEG when it is uploaded, and that JPEG is what the library stores under the photo's name. Photos over 50 megapixels cannot be converted.
On Quick Transfer, a HEIC file sent to the signed-in device has Save to Your images too, and is saved as a JPEG.