https://wccftech.com/asus-shows-off-rog-ddr5-to-ddr4-adapter-board-working-test-unit-demoed-with-z690-apex-motherboard/

ASUS has showcased an interesting DDR4 to DDR5 prototype board that would let you use DDR4 DIMMs on any Z690 DDR5 motherboard.

DDR5 memory is really expensive to get hands-on and that's even if you can find it since it has an impending shortage which won't get better till late next year. As such, ASUS has come up with an interesting prototype board that lets you use DDR4 memory sticks on any DDR5 motherboard. In a video by Lin Dabing Bing, you can not only see the test board but also it running a DDR4 module on a DDR5 motherboard.