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 so we should only replace lz4net on a major version to be safe and mention this on the upgrade guide (see ).
Before the next major, we can introduce support for LZ4 compression on netstandard2.0 by importing K4os.Compression.LZ4 on netstandard2.0 only and keeping the legacy lz4net on net452.