Sometimes devices sold as power inverter that claim to convert 12V to 230V AC (or 110V AC in USA) are not inverters at all, but DC/DC converters that output DC. I would say that calling such device “inverter” is not right, even though it might work with some originally mains powered devices.
I have one bought that device that was marketed as car DC to AC converter, but actually actually is putting putting out DC. I have written more detailed description of it at https://www.epanorama.net/blog/2017/01/12/bizarre-car-to-mains-adaptor/. Here is picture of it when I reused it in some other application.
The mains socket on the front actually puts out DC at a voltage that floats between about 90V to 200V+, so is only suited to universal switchmode power supplies that already convert the incoming mains to DC. It won’t drive a capacitive dropper style lamp or an adaptor with a traditional transformer.
There is a tear-down video of the same, or very similar device in Inside a slightly bizarre car to “mains” adaptor video made by bigclivedotcom goes into details of that is inside this power converter.