For anyone interested in obtaining DDR5 memory for their upcoming Alder Lake build, a leak of certified RAM has surfaced on Twitter, which should provide you with an indication of what to expect when the platform is officially released. 

Even though the list is only a couple of weeks old, it isn't particularly lengthy, as it only includes five brands, three of which are actual DRAM producers and one of which is a subsidiary of one of those companies.  All of the DDR5 modules tested are rated at 4800 MHz and are available in capacities of 8, 16, or 32 GB, with all of the modules utilizing 16 Gbit chips. At 1.1 V, all modules were tested with timings of 40-39-39 and were found to be functional. In this list, Kingston is missing, they are not a DRAM manufacturer, in contrast to SK Hynix, Samsung, and Micron/Crucial, which are all. Intel is categorizing all of the modules as non-ECC, which should put a stop to the assertions that all DDR5 memory is ECC-compliant.

List of DDR5 modules that have been verified to work with Intel Alder Lake leaks