Most PCIe 4.0-based M.2 NVMe SSDs are backwards compatible with systems that only support PCIe 3.0.
Note that the processor is not the only deciding factor; most M.2 NVMe sockets are supported by PCIe lanes from the chipset and Intel's chipsets have lagged behind their processors regarding support for PCIe 4.0.
Note also that the PCIe.4.0 performance numbers reported for these SSDs will obviously not be achievable when connected via PCIe 3.0. Some datasheets will provide different sets of performance numbers based upon having PCIe 4.0 or PCIe 3.0 connections.
Hope this helps,
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