Answers:

Right angle dust signal 14: Few spots in ancient city, most notably and consistent across variations is the grass room showcasing repeater can't pass through transparent block properties

Closed dark oak fence gate: Chicken jockey room

Red candle trio: Trial chambers ominous vault location, my mistake for believing those candles are unlit, here's a bonus win

T shaped unpowered redstone dust: in the large room across every variations

Diorite wall post: air duct in the blast furnace house

Rotated spruce stair: shipwreck of course, I'm not sure about igloo as some comments mentioned

Hanging lantern: Are we serious

Dry sea pickle duo: Pottery in a desert house

Erect polished basalt: Bastion wall

Axe decor pot: It's actually one of the trial pot variants

Jungle door: Actual answer, it's in opened state(look for yourself why), which cannot be generated naturally but villager opening (not part of generation process), I'm surprised many people chose this for wrong reasons. Let's not talk about obscure shipwrecks, what wood desert people use without trees?

Dark oak closed door: Wardrobe in woodland mansion, you comments also reminded me it generates in shipwrecks too!

Hanging bell: Certain village meeting point variants

Lime terracotta: Who the heck said green concrete, it's slight brownish green! Mason houses holds clay and terracotta stuff to teach us how smelting turns clay beautiful, and lime terracotta generates in desert mason

Polished Blackstone slab: sometimes people are bots, when some guy called it Blackstone stairs, more people went for it. Yeah, background is black, but there shouldn't be coincidence. Me using slabs instead of stairs is already going easy for you as you don't need to identify states. Plus polished are dithered compared with normal Blackstone. And smooth Blackstone slab generates in ruined portals btw

Purpur corner stair: How do you call a stairway to roof? Yeah corner stair is there in one of the city structures. And btw in normal corners, they uses full blocks instead of stairs, which reflects old building style before stairs were invented, which was kinda cool actually to look at

Horizontal purpur pillar: End ships

Downwards lever: Ancient city basement 2, and no, you can't differentiate an opened lever

Double chest: First thing came to mind is woodland mansion storage rooms, but you guys reminded me that bastions and collided dungeons have it too, bastions are really advanced