What job is there at Fort Jackson for infantry other than drill sergeant?

"I'm going to Fort Jackson - what will I be doing?" is impossible to answer without additional detail.

If you have the UIC of where you're being assigned, you can perform a lookup in FMSWeb* and then research the unit as they should be listed as a tenant of Fort Jackson*

However, it's a good bet to say that you likely won't be assigned to a field unit, and if not going as a DS, then you'll likely be doing some type of training support assignment.
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* FMSWeb - https://fmsweb.army.mil/
* Fort Jackson tenant units - https://home.army.mil/jackson/units-tenants

Also, basic used to be held at Fort Knox. Now there is an ROTC unit there.

Lotsa Infantry there, what I do not see is the Infantry Brigade that supports the post. Says the 193rd is there, but it is now a BCT Bde. Nor sure where the 197th and 198th are now. 199th is at Fort Benning being Training BDE. So I do not know what a 11x would be, perhaps an ash and trash, MOS immaterial job.

165th Infantry Brigade (Basic Combat Training)[19]

1st Battalion, 34th Infantry Regiment[20]
3rd Battalion, 34th Infantry Regiment[20]
2nd Battalion, 39th Infantry Regiment[20]
3rd Battalion, 39th Infantry Regiment[20]
4th Battalion, 39th Infantry Regiment[20]
1st Battalion, 61st Infantry Regiment[20]

193rd Infantry Brigade (Basic Combat Training)[19]

1st Battalion, 13th Infantry Regiment[21]
2nd Battalion, 13th Infantry Regiment[21]
3rd Battalion, 13th Infantry Regiment[21]
2nd Battalion, 60th Infantry Regiment[21]
3rd Battalion, 60th Infantry Regiment[21]
120th Adjutant General Battalion (Reception)[21]

282nd Army Band[19]
81st Readiness Division[19]
U.S. Army Drill Sergeant Academy[19]
U.S. Army Chaplain Center and School (USACHCS)[19]

U.S. Army Chaplain Corps Museum[19]

Soldier Support Institute

US Army Adjutant General School
The U.S. Army Finance and Comptroller School
US Army School of Music