I've been using this one www.ebay.com/itm/2pcs-DS3231-Real-Time-C...p2060353.m2749.l2649 I've had one in my pi4 since I got it last June so almost a year now. I don't use my Stellarmate OS that much lately but a few days ago I burned v1.57 to an SD card and it picks up the clock fine. No configuration needed.Read More...