EBSCO have switched from using Adobe Digital Editions to Thorium Reader for reading downloaded ebooks.
At the time of writing (May 26) mobile apps for Thorium Reader are still in development and if you try to download an ebook on a mobile device, this is what you'll see:

Fear not! You can still download and read EBSCO ebooks on your mobile device.
The first thing you need to do is download a LCP-DRM compatible ereader app, such as Cantook, PocketBook, FBReader. Some others are listed here. The Digital Library suggests using Pocketbook.
With a LCP-DRM compatible app installed, login to EBSCO ebooks on your mobile device. Then, tell your browser that you want the desktop version of the EBSCO ebooks site.
Chrome
Manage Chrome desktop settings on mobile devices
Edge
- Tap the three-dot menu.
- Select “View desktop site”
Firefox
- Open the page you want to view in Firefox
- Tap the menu button

- Toggle the switch next to to turn it on and off
Now the download message looks like this

You can now download the ebook and open it to read with a LCP-DRM compatible reading app