How much DRAM S0-DIMM DDR4 slot can support?

I'm thinking about buying a laptop and interested in future ungradability. In particular I'm looking into Thinkpad t480s. E.g. here Reddit a person claims to upgrade T480s with i7-8650U to 40Gb RAM (put 32Gb in one available slot + soldered 8). Intel said: Arc Intel

Max Memory Size (dependent on memory type) 32 GB

I guess the reason for this is that when the processor was designed, max size of one memory module was 16Gb. Or what "(dependent on memory type)" could mean? Wiki pages and web search do not promplly answer my question.

Anyway, I'm interested what is the limit RAM of one SODIMM DDR4 slot of that particular laptop model (what specifics except a processor are important?) and one module? Like 1Tb possible?

Edit: practical questions:

  1. Given physical laws and size of the module: 128, 256Gb possible?
  2. How likely that a laptop with same processor with 2 memory slots would support twice max DRAM than with one slot?

The DDR4 standard allows memory modules up to 64GB.

Whether anyone has ever made a module that large or a memory controller that can support that large modules is another thing - as these may have not existed in the year the CPU was released so they may have only verified it works up to a certain size, but it might unofficially support anything you can fit into the slot, if the module has a supported timing and memory organization (e.g. single/dual rank).

The CPU also supports both DDR4 and LPDDR3 types of memory and this type will define the maximum memory amount, as DDR3 allows for smaller modules than DDR4.