You can get Z690 DDR4 boards. That's what I had to resort to so we could test our software on the i5-12600k. Getting a CPU cooler with an LGA 1700 compatible bracket was actually the hardest part.
One downside of this current Alder Lake release might be the fact that the Z690 motherboards are much more expensive than the AMD's current mainstream motherboards. The CPU might be a tad cheaper but overall it might not be worth it (well, until more affordable motherboards appear).