Having designed a bunch of bikes on the market and having welded a bunch of my own I’m not convinced that speed wobble is the result of 1 thing but the product of multiple things gone slightly wrong. I’m pretty sure that small changes to the system will provide a resolution.
Wheels/Tires (imbalance on a 1100g set of wheels has more impact than on a 1800g set of wheels)
Static Position ie contact points
Dynamic Position ie where’s your CoG when you descend or sprint or whatever.
Fork offset (rake)
Weight (the bike’s or yours)
Of course, addressing these things should be done only after you triple check your bike for loose or compromised components.
My gut feeling is that if your bikes are in perfect working order then you need to look at you. What are you doing to contribute to this? Can you make position adjustments? If not, you need new bikes.