Actually, the type of low-power-consumption memory (LPDDR5) used with Apple silicon typically can't be installed in DIMMs/slots. The same is true for the new Qualcomm Snapdragon X Elite. However, I do remember reading earlier in the year that a new LPDDR5 format that can be installed in removable "slots" is/was under development but that may be too soon for use in Apple's current generation of Macs. Maybe next year in the Mac Studio or Mac Pro?Many of them PC Minis will also have room for slotted RAM and at least 1- often 2- m.2 slots for competitively-priced storage too. But Apple can't/won't do that. Why? Not because they can't.
Here is a link to more information on this development:
https://www.crucial.com/articles/about-memory/what-is-lpcamm
However, it looks like this new type of memory "stick" is pretty expensive right now. A 32GB module is currently $175 from Crucial/Micron, while 64GB is $330. Meanwhile two sticks of 16GB DDR4 SODIMM memory (32GB total) is just $66.