For your syndication criteria and the greatest level of simplicity, I’d recommend looking at Micro.blog first. There are some other potential options listed at https://indieweb.org/Quick_Start.
If you’re a bit more technically adventurous, you might look at WithKnown or WordPress. The trouble is that there are lots of methods for syndicating and having control over what your content looks like. Your mileage may vary depending on what platform you choose and what type of automation and flexibility you’re after.
As an example, my own WordPress site has at least three different ways to syndicate to Twitter (not counting doing things manually), and how I do it depends on the content, my mood, ease-of-use, and what I’m looking for on the other end.
IndieWeb chat is also a good place to ask for help depending on what you’re looking for or for drilling into the specifics of what is available on individual platforms.
Syndicated copies: