When I first heard of the Somnium it sounded like perfect specs on paper, but when I saw the price... oof... Pimax Crystal Light has a much more attractive price, but from what I've read it seems to have horrible quality control and that it requires buggy proprietary software, which might mean it'll never work on Linux.
Hope Valve could make an Index v1.5 which just has updated screens with slightly higher res and keep the the ~€1000 price for a full kit. But with the electronics shortage and inflation which happened since the Index was released it might not be possible.