According to this post:
V10 was supposed to be supported until the end of 2020.
But it has been non-functional for at least a few weeks now due to lack of print formats. There are none in it to be used for regular sales invoices or purchase orders. These being the most important functions of the system, the version is disabled and no longer useful.
This does not match up with the promised stability support.
So what is the real answer?