Single RAM slot is a big F you. They picked a 8 core part with support for only one DIMM, instead of almost anything else that could have taken 2 RAM sticks
Very specifically made sure to leave room for a new TS-x64
I would miss the PCIE slot but I could do without.
https://nascompares.com/2025/09/09/qnap-qu405-qu605-and-qu805-nas-revealed/