Assuming you have a 240 volt inverter and you are using a Victron autotransformer to supply 2X120 legs to the panel, you will need a second autotransformer to supply 240 volts to the inverter. The second autotransformer will convert the 30 amp 120 volt to 240 volts (at 15 amps). This is the setup we use in our motorhome and it works very well. You will need to adjust the input current on the inverter to 15 amps, I usually set it to 14. I like having a Digital Multi Control, it makes this very easy although you can do it with a Cerbo.
As far as using an autotransformer in an RV, it’s my understanding NEC defines an autotransformer as “a type of electrical transformer with a single winding acting as both the primary and secondary winding.” As the Victron autotransformer uses two windings, both a primary and a secondary winding, it is not an autotransformer as defined by NEC and therefore acceptable for use.