Inspiron 3668 Desktop, GPU upgrade, GTX 1050 Ti?

Unknown. The Inspiron Desktop 3668 240w PSU (power supply unit) was never tested on retail GTX 1050. You would have to get the Dell OEM version =
1MPR3 AMD R9-360 (2GB, DP/HDMI/DVI-D)
24K8H Nvidia GTX 1050 (2GB, DP 1.3/HDMI 2.0/DVI-D)
8CCF1 Nvidia GTX 1030 (2GB, HDMI/DVI-D)
8MXMJ Nvidia GTX 750 Ti (2GB, mHDMI/DVI-D/DVI-I)
J27RG Nvidia GT 730 (2GB, HDMI/DVI-D/VGA)

Is there somewhere I can find a list of which graphics cards have been tested with which models of Dell computers? Where did you find that list you posted?

The issue with 3668 is that the machine has very narrow slot.  The problems with working are PHYSICAL DIMENSIONS as well as POWER USE. Full length cards DO NOT fit into the case.  There are users who use a moddiy adapter and then remove the stock power supply and put a standard unit OUTSIDE the case running the wires thru the hole left behind when the stock unit is removed.

8CCF1 Nvidia GT 1030 (2GB, HDMI/DVI-D)

https://www.dell.com/en-us/work/shop/msi-gt-1030-2g-lp-oc-graphic-card-2-gb-gddr5-pcie-30-x16-low-profile-hdmi-displayport/apd/aa362018/graphic-video-cards

There is an Ugly hack that allows PSU upgrade.  Its called take internal power supply out and use a MODDIY 24 pin to 8 Pin adapter cable and run the wires to the inside thru the hole left by removing the internal power supply.

Suitable for Dell OptiPlex 3020 / 7020 / 9020 /

Precision T1700

Inspiron 3650

https://www.moddiy.com/products/Dell-Inspiron-3650-PSU-Main-Power-24%252dPin-to-8%252dPin-Adapter-Ca...

People have been able to make it into a gaming system with a fair GPU.

Even Austin however does not recommend this system for a gaming platform.

https://www.amazon.com/Gigabyte-Radeon-Windforce-Graphics-GV-RX460WF2OC-4GD/dp/B01K1JVCRE/

https://www.youtube.com/watch?&v=J81h1dHNwDk

The 3650 and 3668 vs 3670 or 3847 or Optiplex 9020.

Thank-You just asking,not a gamer, last game I played was at an arcade, Miss Packman? my nut on the top of my VGA plugin fell off so I might as well get a higher watt power supply like a 450 to 550 incase later on I want to do something. I also have 12 gb memory and I can install up to 16gb.So I need 1 stick of 8...I have 1-8 and 1-4. what about the core? Just want to be able to do whatever? Hard drives? what else. What do uo recommend. I also have aHD 6450 afterburner. says-pci expressone x 16,400w pwr supply,1gb memory,dvd playback requires DVD drive, and blue ray playback. do not want anything outside of computer. also usb for backup for w 10 and do u back up files separate, have digital cloud and others. i know its a lot, bought new, in june of 2017, got sick in august 2017, just started pc back up in june 2019? do not know computers,HELP PLEASE

Pascal based GT1030 is a 40W card and works in almost all models EXCEPT Micro and USFF and AIO.

You can order that with the unit from dell

8CCF1 Nvidia GT 1030 (2GB, HDMI/DVI-D)

https://www.dell.com/en-us/work/shop/msi-gt-1030-2g-lp-oc-graphic-card-2-gb-gddr5-pcie-30-x16-low-profile-hdmi-displayport/apd/aa362018/graphic-video-cards

https://www.youtube.com/watch?v=2y32mBdZHJY