There are some investigations about Flow ongoing. This task merely lists what are the blockers to avoid regressions in TWN-specific matters.
It's not going to list blockers which are such for any wiki, nor to be a full list of requirements, nor to list "nice to have" which we never had or can't have in LQT or wikitext or others.
I've read the documentation for Flow but it didn't address most of the TWN workflows. Some more things to check are the TWN reports against LQT (minus fatals and exceptions, usually LQT-specific).