Unable to find Dual Rank 4GB of ram for DS220+

[ed]

Yes, you may not find them as easily. Usually, they only produce dual RAN RAM, when those memory chips do not fit on a single side. Usually with bigger capacities. Otherwise, you will more often see single-rank RAM.

I hope this video help https://www.youtube.com/watch?v=gRm-T5oN91E

ADATA Adata Premier 4GB AD4S2400J4G17-B - https://amzn.to/3sNsql8
TimeTec 8GB 76TT26NUS1R8-8G - https://amzn.to/3wqVtgC
Sabrent Memory 8GB SB-DDR8 - https://amzn.to/3G0XeEg
Crucial 16GB CT16G4SFD8266 - https://amzn.to/3NjJjvm
TimeTec 16GB 76TT26NUS2R8-16G - https://amzn.to/3G08aC4
Sabrent 16GB SB-DDR16 - https://amzn.to/3Pta6HE
Transcend TS1GSH64V6B 8GB - https://amzn.to/3PzU3YL
Transcend 2GB TS256MSH64V4X - https://amzn.to/3wvjN0E

Other Memory that has been tested and worked:

Kingston KVR26S19S6/4 4GB - https://amzn.to/3wtpMDp
AM-D4NESO-2666-4G 4GB - https://amzn.to/3wtpMDp
Crucial CT4G4SFS8266 4GB - https://amzn.to/3NmzOvB
TimeTec 76TT26NUS1R8-4G 4GB - https://amzn.to/3wr1dHc
Transcend M2666HSH-4G 4GB - https://amzn.to/3wH2p7Y
SK Hynix HMA851S6CJR6N 4GB - https://amzn.to/39C1r56
SAMSUNG M471A1K43CB1 8GB - https://amzn.to/3Mx3uWK
Crucial CT8G4SFS8266 8GB - https://amzn.to/3wtwadR
ATech AT8G1D4S2666NA0N12V 8GB - https://amzn.to/3LsUkZZ
SAMSUNG M471A2K43CB1 16GB - https://amzn.to/3yMnMaN
ADATA AD4S3200716G22 16GB - https://amzn.to/3NHpI8X