I created several .tar.zst files using ark 19.12.3. Now after the update to 20.04.0 I can't open those archives as well can't create such archives.
Ark doesn't list zstd in the plugins.
My workaround for the moment is to use tar on the command line as this is still working with zstd.
I hope this is the right form to report a bug, it's the first time I need to do this in Solus.