Hi silverpunk,
I’m not personally familiar with the Ikea beds and furniture isn’t my area of expertise but I did take a look at the assembly instructions and it has a center beam (which needs to be picked up separately but is included in the price) with center support to the floor so if you are OK with particle board it should be suitable for either mattress with the laxeby slats.
I can’t see how this one is constructed or the details of the slatted surface so I really can’t make any comments about it.
There are a few sources for platform beds and headboards that may also be worth considering at the end of the foundation post here.
Phoenix