Which missiles will be used for VLS as they can not be launched from torpedo tubes?
For the first or second VLS?
For the first, think of it as a provisional space. Interpreting the Navy's habit of incorporating future visions into their current designs, they may have left a space where Gezgin or others can be accommodated first, then whatever comes next in the future.
As for the second, who knows. There are only rumours.
Technically it can be done, but I think sacrificing Torpedo tubes is almost never a good idea for diesel electric boats. I am firmly against it. Because it doesn't have the large torpedo room of SSNs. So, you gotta be really careful with priority management and don't want your boat to run out of its primary weapon.
And interpreting the inclusion of the VLS module in the Milden, that is a complex and rough way that the Navy had opposed earlier, the Navy should have finally considered torpedo tubes as rather flexible points to use expendable UUVs, torpedoes and Sub-Atmaca (short range set of weapons) and others, while shifting the surface attack to VLS (long range set of weapons).
There may also be another reason related to Gezgin's dimensions, which were recently updated, making torpedo tubes unnecessarily long and unfeasible, thus prompting the switch to VLS. However, I am sure that either Kara Atmaca (or maybe SOM) will get a submarine version or Gezgin will get a 'Lite' version.
Speaking of Milden, the VLS launch weapons refer to an era beyond 2035, so I think there are plenty of opportunities to do a fictional experiment on what can be done with these VLS.
This post only contains information from open sources or just wild thoughts, nothing concrete.