MIF and SVG output support have not been restored, yet.
Auto table layout is not implemented, yet.
Footnotes may overlap with text of the region-body in multi-column
documents.
Space resolution does not work between footnote regions.
There's a problem involving nested block-containers and
reference-orientation 180/-180 (Bugzilla #36391)
block-containers with no height currently don't create a fence for
spaces as they should (they behave like a normal block).
Preserved linefeeds in fo:character are not handled correctly.
An empty block currently produces a fence for stacking constraints
which it shouldn't.
There are several small problems around white space handling.
leaders with leader-pattern="use-content" may not work as expected.
If two consecutive pages don't have the same available width, the
content currently isn't properly fit into the available space on
the new page.
background-images on page-number-citations are not placed correctly.
Not all FO elements can be referenced by their "id", most notably:
table-body, table-header, table-footer and table-row.
Column balancing in multi-column documents may not work as expected
(Bugzilla #36356)