Have you tried to install the original CPU (I assume you had a CPU prior to the 1900X). Judging by the beep table, I would say you have 3 different errors.

3 beeps is Motherboard Chipset

6 Beeps is Video Card/Chipset

1 Beep is Motherboard or possible BIOS or ROM error.

Considering that you installed a new CPU, have you tried pulling the CMOS battery (coin cell), leave it out of the system for 15 minutes, then instead of reinstalling the old battery try a new battery. A bad battery would certainly cause the system to not POST and possibly give you other errors.

https://www.dell.com/community/Alienware-General-Read-Only/Alienware-Beep-Codes-Table/td-p/5588971

I just tried different DDR4 memory from another computer and it gave me 4 beeps.  I didn't think the memory was compatible but I figured I would try it.  Some say if your motherboard will beep twice with no memory and 4 times with incompatible memory that the motherboard is ok but I really don't know.

I am wondering if all the beep codes combined mean something specific that only Alienware knows?  I never seen anyone have a issue like this.

The original CPU is N/A.

I replaced the CPU in my Predator back in the day without issues-I am perplexed now.  Suspect the processor is a newer generation than the A3 can handle and I need a older CPU first to update the BIOS?  I sure hope that is not the case.