XSLT 2.0 conformance
From Saxon 9.8, Saxon no longer offers an XSLT 2.0 processor: the product now implements XSLT 3.0 only, and is not tested for XSLT 2.0 conformance.
XSLT 3.0 has a very high level of backwards compatibility with XSLT 2.0, so all existing stylesheets should continue to run. The only significant difference when you process a 2.0 stylesheet with a 3.0 processor is that you will no longer get errors if you use constructs that are permitted in 3.0 but not in 2.0.
There are a few very minor incompatibilities between XSLT 3.0 and XSLT 2.0 listed in the W3C specifications: for example, some error codes have changed.