On older phones, it wasn’t possible to get Android support on a Sailfish phone unless it had official support from Jolla, i.e. it had to be the Sony Xperia-phones or one of the older Jolla phones. Now you can buy “AppSupport for Linux Platforms” in the Jolla store. Does this allow users to add Android support to any phone running Sailfish (or Linux in general)?
No. The community have asked Jolla for this, and I think it could be in their plans, but nothing has come of it yet.
Community ports tend to have Waydroid built against them, and this will provide some level of Android app support, but older devices may be stuck without due to the kernel.