Hyundai and Kia added official GrapheneOS support to their apps months before Volkswagen banned GrapheneOS:

https://discuss.grapheneos.org/d/31697-myhyundai-app-has-official-grapheneos-support

Pressure from Volkswagen customers on them can achieve the same thing. There's no legitimate reason to ban GrapheneOS so they'll undo it with pressure.

myHyundai app has official GrapheneOS support - GrapheneOS Discussion Forum

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@GrapheneOS Just don’t buy Volkswagen.
@Herman People already bought those cars and need them to stop banning GrapheneOS so a pressure campaign is needed. It worked with other companies and will work again.