Hi @Urrutia Jacome, A ,
App services runs on a sandbox and therefore you won't be able to install any custom software. If your referenced DLL isn't able to run using one of the available runtimes, you would be to deploy your application inside a custom image and host your container your app service. You will have to create a new Web App for Containers app service though. For the long term, I would also encourage submitting feedback to the product group asking for additional JDK/JREs to be installed.
Regards,
Ryan