I agree with PCR, if 1803 won't install, try backing down through the versions: 1709, 1703, 1607.
You can use this tool to supposedly download the ISO files from MS (I have not seen independent confirmation)
Download ISO files and disc images with any version of Windows and Microsoft Office (100% legal)
https://www.digitalcitizen.life/easiest-way-legally-download-iso-images-windows-and-office
A developer has created a small free tool, Windows and Office ISO Download Tool, that assists you in downloading the ISO disc image for any Version of Windows or Microsoft Office you want, straight from Microsoft’s servers. This article tells how to find and use this tool
I do have a link to another site, in Russia, if you really want it.