lz4net has been deprecated and moved to K4os.Compression.LZ4. The new library specifically exposes an API to read files created with the "legacy" library (lz4net). Also the new library is listed under the "Interoperable ports" section while lz4net is listed under the "Custom ports" section.
For these reasons, compatibility between these two libraries is not 100% guaranteed and we should add this change on a major version to be safe and mention this on the upgrade guide.
Users should not be impacted by this whatsoever since this is used internally by the driver and the user doesn't ever interact with lz4 directly through the driver.
LZ4 Compression is not supported on .NET Standard. See this issue
If needed, we could support LZ4 for .NET Standard 2.0 (in a different target) with this new library.