If you need more ram but not a lot of CPU a used thin client can work, i use a HP t630 since 6 months now with only nextcloud and storage, has 2 ddr4 slots and 2sata m.2(not Nvme) for Expansion. Again its a 4core Pre Ryzen AMD chip so don’t expect any Wonders. https://www.parkytowers.me.uk/thin/hp/t630/ this is a good side for this and other thin Clients.
Edit: according to HP the idle Power consumption is ~12w
kind of… a “AMD GX-420GI SOC: quad-core APU” the one with no L3 Cache, in an Thin Client and 8Gb Ram. old Laptop ssd for Storage (128GB) Nextcloud is usable but not fast.
edit: the Best thing: its 100% Fanless