It's not showing up under my installed extensions.
Topic on Extension talk:Genealogy/Flow
Appearance
It is, but the GraphViz extension is not; other fuctions still work correctly.
I replied to your question at User talk:Samwilson#Not working in Mediawiki 1.34.
Moving things to Mermaid, which is included in Mediawiki now and works (unlike Graphviz) would be a good. It would also offload rendering to the client, an important consideration for busy wikis.
Mermaid support is now available. Use the format=mermaid
for the tree parser function.