Memtest86 is a great build companion as well, it will display populated slots and run memory testing, which I've found is a good overall health indicator, and always run it on new machines.
A couple years ago we bought a new Dell server and after 24h of memtest it would fail one of the last few tests, and identified a particular memory module. We went back and forth with their support, they didn't want to replace the module unless their built-in memory test, which only ran for ~30 minutes, said the module was bad. Finally we contacted the sales people and asked "How long do we have to return the server for a refund?" and shortly after that tech support agreed to send us a replacement module, which did end up passing memtest.
Another option is the related memtest86+ (https://www.memtest.org/), which can be found as a package on many Linux distributions (and the package often adds it to the grub menu), and on some Linux distributions it's even on the installation DVD (so you can use it to test the memory before installing).
For a while, it didn't run on UEFI (it required legacy boot), but recent versions now run on both UEFI and legacy BIOS boot.
https://www.memtest86.com/
A couple years ago we bought a new Dell server and after 24h of memtest it would fail one of the last few tests, and identified a particular memory module. We went back and forth with their support, they didn't want to replace the module unless their built-in memory test, which only ran for ~30 minutes, said the module was bad. Finally we contacted the sales people and asked "How long do we have to return the server for a refund?" and shortly after that tech support agreed to send us a replacement module, which did end up passing memtest.