Changes in Aimy Sitemap from version 3.20.2 to 3.20.6 are minor code optimizations and bug fixes.
For example we optimized link handling for multilanguage sites, improved canonical link recognition and updated the Polish translation.
With Aimy Sitmap 3.20.6 we had to remove Yandex notifications as this feature is no longer supported by Yandex. From now on, sitemaps can be added in Yandex's webmaster tools. Have a look at their sitemap documentation: https://yandex.com/support/webmaster/indexing-options/sitemap.xml.