Hello Lustig12

The heatspreader (IHS) on the Core i9 is actually not soldered but glued to the edges with a kind of silicone adhesive. However, this is also done with "soldered" processors.
The only difference to "soldered" processors is that between the die (the actual silicone of the processor with all the transistors) and the heatspreader, a heat-conducting paste is used instead of indium solder. The only disadvantage of the heat-conducting paste is higher temperatures in the processor cores, as the paste conducts heat more poorly than indium. Both variants are absolutely dust-proof.

Greetings Chris

The CPU still has the fan on it -> no, dust should not be a problem.

You have misunderstood something. The heatspreader (what you see on the surface, so to speak) and the die are not soldered, but there is only cheap thermal paste on it. No dust will get between the heatspreader and the die. By sealed you probably mean soldered, it's actually not. In general, the 7900X is not worth it, the 1950X is actually always better and the 1920X mostly better.

actually, i would be really happy to get answers from specialised staff instead of buyers who pursue a strategy and end up in an opinion debacle where it is better to shut up than to get involved. no offence intended.