How do I let people easily subscribe to my blog's updates via RSS?

Hi,

I’m trying to add an RSS widget to my blog, which is not published yet (i.e. “Coming soon” message is on).

This is how I’m attempting to do it in my Activello theme:
1 - Go to Customize >> Widgets
2 - Add a Widget >> RSS
3 - Under RSS, add the following RSS feed URL:
http://sparkandspoon.com/feed/rss/

I get this error:
RSS Error: This XML document is invalid, likely due to invalid characters. XML error: Undeclared entity error at line 4, column 31

I have also tried these other URL formats, and got the same error message:
http://sparkandspoon.com/?feed=rss
http://sparkandspoon/?feed=rss2
http://sparkandspoon/?feed=rdf
http://sparkandspoon/?feed=atom

Please help! Thank you!

Hello there,

I hope you are doing well today.

This could be an issue with the plugin, please try using another RSS feed to test it or try another plugin. Here are a few:

Best Regards,
Support