What kind of bike/frame do I need?

disc brakes but quick release drop-outs and 135mm rear spacing, rack and mudguard mounts, maybe more traditional geometry rather than sloping top tube, 1 1/8 non-tapered steerer forks. It'll mainly be used for touring, but I'd like it to not be an absolute tank

Didn't tonnes of bikes used to fit this description? My Pass Hunter does. Now they'll all be Thru Axle, tapered, flat mount, etc etc. So second hand for sure.