If your just growing a lemon tree in your back garden then an air layered or tree on its own roots is ok.
there isn’t an orchard in the world that grows lemons commercially on their own roots. They have very little pest or virus resilience grown like this. This will all become clear years down the line I really would not recommend farming any citrus tree if it is not on a good compatible rootstock.
another note on the Eureka is that Eureka seedlings are used in top end nurseries around the world for indexing.
this is virus testing, wils another tree used. They use the Eureka for this method because it has very limited pest , virus resistance and shows up viruses on new grafted trees quickly.. it’s definitely not to be used as a rootstock.
all this information is out there on the internet.. very easy to find.
please I urge anyone going into farming Lemons or other kinds of citrus to do your homework first.. because planting them on their own roots will end badly and you will lose a lot of trees down the line.