I don't have lithium but have given it some thought including this issue if I where to upgrade. Bottom line yes you don't wan't a normal auto battery combiner. I know some use a manual combiner so they can charge from the alternator if needed and watch the system as necessary while driving.
To automatically charge from alternator you would need a dc-dc charger like a Sterling. I wish someone would make a nice two way dc-dc charger so alternator can charge house and solar/shore can charge chassis with proper battery profiles on each. I haven't found that yet.
Magnum smart combiner might work too.
Victron makes an interesting BMS that works with their lithium batteries for charging from alternator but requires as DC-DC converter for house loads for reasons I am not entirely clear on:
https://www.victronenergy.com/upload/documents/Datasheet-BMS-12-200-EN.pdf
