Unrecognized Video Card

@KerriMor  It sounds like you've found graphicscards.sgr?  (If not, the default install location is Program files (x86)\Origin Games\The Sims 3\Game\Bin.)  Open it—if you're asked to choose which app to use, Notepad works fine—hit crtl-F, and search for 1309.  That will bring you to these lines:

card 0x6920 "AMD Radeon(TM) R9 M395 Graphics" $cardLevelMedium $resolutionHigh
card 0x1309 "AMD Radeon(TM) R7 Graphics" $cardLevelMedium $resolutionHigh
card 0x130C "AMD Radeon(TM) R7 Graphics" $cardLevelMedium $resolutionHigh

(with spaces in front of each line that aren't copying over properly here).

After the R9 M395 line, hit return, and add the text in this box:

    card 0x15D8 "AMD Radeon(TM) Vega 8 Graphics" $cardLevelHigh $resolutionHigh

I'm guessing on the card level, but if the settings are too high, you can turn a few down in-game, or else change the "$cardLevelHigh" to "$cardLevelMedium" above.

Save, quit, and launch the game once.  Then you can check whether the card is now recognized.  Go into Documents\Electronic Arts\The Sims 4, open config.log, and scroll about 30 lines down to where your card is listed.  It should say [Foune: 1, Supported: 1] now.

Keep in mind that any time you patch or repair the game, graphicscards.sgr will revert to its original form, and you'll need to redo the edits, at least until EA adds your card to the database.  So you might want to make a backup of the file and replace it when necessary.