Not once has the xxF shared between models have been huge die reforming changes. So, Lucienne pretty much has to be identical to previous versions. Thus, Renoir and Lucienne is the same die. Just like Zambezi<->Vishera, Trinity<->Richland, Kaveri<->Godavari, Carrizo<->Bristol, Raven<->Picasso, Summit<->Pinnacle, etc so on so forth.Renoir as far as my deep dive does support LPDDR5, but since it doesn't support DDR4 ECC(144-bit({64+8} x 2) PHY) it might not support DDR5 ECC(160-bit({32+8} x 4) PHY). I am not sure if DDR5 supports ECC-less implementations. If it does it also supports DDR5 up to 6400 Mbps.
Renoir uses the DCT IP w/ LPDDR5/LPDDR4X/LPDDR4 and no-ECC DDR5(if possible)/DDR4 combo phy/controller. Do to the January 2020 update for the LPDDR5 spec, it was probably delayed(to Lucienne) or canned(for Renoir).