Is there a quill delta format to html converter for flutter?

You can try this to convert.

var QuillDeltaToHtmlConverter = require('quill-delta-to-html').QuillDeltaToHtmlConverter;

// TypeScript / ES6:
// import QuillDeltaToHtmlConverter from 'quill-delta-to-html'; 

var d_Ops =  [
    {insert: "Hello world\n"},
    {insert: "This is colorful and joyful", attributes: {color: '#f00'}}
];

var config = {};

var converter = new QuillDeltaToHtmlConverter(d_Ops , config );

var html = converter.convert(); 

Source: https://github.com/nozer/quill-delta-to-html