Is there a chart/statistic which versions of Shopware 6 are used by online shops actually.
Background: developing custom plugins, it's hard to cover all versions from 6.1 - current (6.4)
I would suggest supporting the releases since the latest major release 6.4, which has first been released 1 1/2 years ago. That's ample time for users to have updated to one of the minor releases since then. When you offer plugins in the community store you'll get an overview which Shopware versions your plugin is used with. Looking at the data of my plugins I can tell you that the vast majority is now at 6.4. Without breaking changes it should not be a problem supporting all 6.4 releases and with the 6.5 major release coming next year you should be able to cover a significant userbase by supporting both the upcoming and the current major release.