You have to update to the latest bios and you have to turn secure boot off.

If your power supply DOES NOT provide at LEAST 140W on the 3.3v/5v rails this may be the other problem. If the card is too long you will have to hack out the drive bays and put them somewhere else because the inside does NOT accomodate 12 inch cards.

EVGA 750B1 or EVGA 700BR meet that spec.

https://www.evga.com/products/product.aspx?pn=100-BR-0700-K1

https://www.bestbuy.com/site/evga-br-series-700w-atx12v-eps12v-80-plus-power-supply-dc-dc-technology-black/6346160.p?skuId=6346160

https://www.youtube.com/watch?v=13vY67_sXbg

It seems DH67M01 is for both Vostro 460 and XPS 8300. Possibly Dell sold the same motherboard in different case and market it as two different model.  XPS8300 bios is legacy only no uefi, and no secure boot option. It is probable V460 bios is just another repackaged legacy bios the same as XPS 8300 with just minor cosmetic differences.

RTX2070 being a modern gpu may not work with pc that has legacy bios only.  Consult your gpu vendor support site to see if legacy bios is supported.  It is probably good idea to consider a faster pc that better matches RTX2070 than the current Sandy bridge cpu in DH67M01.  The GPU and cpu do not work well together; the cpu is too weak for the gpu.

Your processor is too weak for this graphic card on 1080p resolution

Intel Core i7-2600 (Clock speed at 100%) with NVIDIA GeForce RTX 2070 (Clock speed at 100%) x1 will produce 59.18% of CPU bottleneck on 1080p resolution. Everything over 10% is considered as bottleneck.

Follow the instructions in this post:
https://www.dell.com/community/Vostro-Desktops/Vostro-460-Successfully-Installed-Nvidia-1650-GTX/m-p/7636877#M4202

I have a 1660ti and it worked for me.

Update to current bios and the rest is secure boot off.

YMMV

If you USE ONBOARD VGA AND MONITOR you WILL SEE BIOS using the integrated VGA graphics. Once Windows 10 boots and is online, It will download the GTX 1650 drivers.  You can then switch to hdmi to dvi cable into an appropriate monitor.

This guy did just that with Vostro 470

He wasn't able to get it working with old bios.

Newer 460/Dimension 8300 may not work if you need F2 bios access.

GIGABYTE GeForce GTX 1650 4 GB D6 Windforce OC Graphics Card is works

https://www.gigabyte.com/Graphics-Card/GV-N1656WF2OC-4GD-rev-10/support#support-dl

https://www.youtube.com/watch?v=13vY67_sXbg

Bios does need updating 

Dell XPS 8300 and Vostro 460 System BIOS

Fixes  Updated VBIOS from 2098 to 2119 - Enabled C6 as default - Updated Intel MRC code to rev 1.2.2

https://dl.dell.com/bios/TR-A06_QS.EXE

View full driver details

https://www.dell.com/support/home/en-us/product-support/product/vostro-460/drivers

So sadly this CPU is not good enough for a 2070  in PC builder terms we call this a bottleneck it’s when your CPU holds back your GPU me personally the highest you should put in that system is a 1080TI I use a GTX660 2GB from ASUS but the best option would be a GTX 970 in my opinion I used to use a 970 before it stopped working and it worked great with very little bottlenecking  and LGA 1151 is very limited on CPU options the best LGA 1151 CPU is a Intel core I7-3770K also I use a 600WATT powersupply and 24 GB of DDr3 ram