Simply Static is a nice WordPress plugin which converts your site to a static version where you can use it without Php and DB support. It generates a static version of your site or blog on-demand without doing any modification to the existing setup in the format of the zip file.
Host your blog in pen drive without any Web server requirement. Amazing! right. Yes, it is. The recent version is now under new ownership it seems. When I tried to fetch the static version I am getting the following debug error.
Uncaught RuntimeException: Not valid HTML fragment! .wp-block-button__link%7Bcolor%3A%23fff%3Bbackground
Tried many options like changing the theme etc. At last found issue. Gutenberg!. Disable Gutenburg and Simply Static started working.