https://quarry.wmflabs.org/query/25866 shows the linter counts in all high priority categories in namespace 0. It shows that except for frwikiquote , all other wikiquote wikis could probably be switched over to RemexHtml soon. There are a few wikis where there is some category with just over a 100 entries. But, I don't think we should let that stop us from doing the switch. Since Linter is going to be around, those wikis can make the fixes after the switch since the breakage will be a lot more obvious.

frwikiquote has a large number of html5-misnesting errors because of interaction of {{citation}} and <poem> tag. The poem tag generates a <div> wrapper and the citation tag wraps a span tag around its parameter which causes a <span> to wrap a <div>. ?action=parsermigration-edit shows that this doesn't cause any real rendering difference, but this is a buggy nesting nevertheless. Maybe the citation template should be fixed to handle this scenario?