Followup on my ram upgrade, detail in comment : r/qnap
Amazon.com: QNAP TS-453Be-4G-US (4GB RAM Version) 4-Bay Professional NAS. Intel Celeron Apollo Lake J3455 Quad-core CPU with Hardware Encryption : Electronics
64 gigs of RAM upgrade for TS-873A worked first time : r/qnap
QNAP Presents TS-253Be and TS-453Be with M.2 and 10GbE Expandability
QNAP TS-453Be 4 Bay NAS 16GB RAM Upgrade - YouTube
RAM for TS-453Be : r/qnap
Qnap TS-453Be review: A versatile and future-proof NAS | Expert Reviews