Where are the download images for Android?
It seems like for Samsung devices the image download servers are available but there is no user interface to select an image for download. According to XDA blog there is a new Python based command-line tool that allows to search and download Samsung factory images:
https://github.com/nlscc/samloader
As the download information and the firmware images are original downloads from Samsung servers they can be considered trustworthy.
The original article from XDA:
https://www.xda-developers.com/samloader-download-updates-samsung-galaxy/