If even supports 3,600 Mhz ram with the latest bios update. As for 3400 Mhz, it technically speaking runs at 3,466 Mhz. Some people in the past reported issues with this, but it looks like an older bios update fixed that.   If you purchased it directly from DELL it will be tested before being shipped, and all items will have been validated to work for your chosen configuration.  
I recently bought an aurora R10 Ryzen 9 5900 RTX 3080, with a 64GB Dual Channel DDR4 XMP at 3400MHz, but  I found that people referred that this combination of CPU with a memory of 3400MHz is not worth it bc aurora r10 omen mother boards only support  up to 3200MHz, moreover, some has reported instability issues. I am new in this matter so I would like to know if someone can help me clarify. Did i select  the right parts for the R10?
Aurora R10 Ryzen 9 5900 RTX 3080 10Gb