Zedwick has asked about the rates.
Mining (Based on several hours of mining, personal records):
Conventional eff5 strip mining with a mixture of a little bit of caving without haste 2 have provided me with
226 iron ore per hour (alongside with other resources). In case you are wondering the rate is very comparable with diamonds (about 2 stacks of ore per hour, ore! with silk touch!).
Full clear with eff5, haste 2 will yeild about
240 iron ore per hour.
Vertical strip mining with haste 2, eff 5 specifically hunting for iron ore (This i have tested with a timer per chunk cleared). Got on average
672 ore per hour, personal best clearing time will result in
753 ore per hour. Theoreticall maximum would be about
960 ore per hour. Method requires potions, rockets and overall very intense and stress inducing, would not recommend, if you care about you own health and are not desperate.
In addition double layer (for dirt+an actual layer) quary machine will limit only at coolection speed and chunkloading distance. In case of manual collection it will yeild
over 1000 iron ore per hour, but I am pretty sure quary machines are bannable on the server.
To sum up it's safe to assume that mining will yeild on low end
200 and 700 iron ore per hour on high end.
End raiding (Based on personal records of about 15 hours):
83.3 iron ingots per hour alongside many other resources. Probably will need to be multiplied by 2, if purely hunting for iron.
Bartering (Based on calculations and expertise of people, who dig the code)
1 pigling has a rate of
35.46 iron ingots per hour as of 1.16.1 and will have
33.4 in 1.16.2. aat the cost of 600 gold ingots for the same time interval. Normal fully afkable playerless sorter can only handle 2 piglins max. As of an absolute min-maxing on the pure trade it will yeild over
6k iron ingots per hour (
https://www.youtube.com/watch?v=re3OKwY2UKs), but as mentioned in the video the setup is absolutely unreallistic and no gold farm can actually support it. Fully juiced up gold farm on the roof of the nether can only feasibly support at most 10 pigling trading simultaneously, while requiring looting 3 and crafting of both gold and iron ingots (say hello to an autoclicker).
In other words a realistic bartering system with gold farm will yeild
30 to 300 iron ingots per hour. Iron from the bartering is very likely to be used only, if one plays in nether only world.
Zombie farming (Based on calculations of typical general mobs farms)
Zombies have a 3.8% chance to drop iron with looting 3 (not sure if it competes with potatoes drops). Typical mob farms have a cap of around 20k drops per hour, which translates into about 16k mobs per hour. It's possible to supress skeltons (almost) and spider spawning, so about 8k zombies per hour, so
~300 iron ingots per hour, maybe?
On hard it will actually increase by 8.3% due to reinforcments. Here might emerge a concept of reinforcement based farm. I don't think anyone sane has attempted to build one, but it could potentially at the very least quadruple the rates?
So about this one I will speculate that the farm can produce
maybe 300 to 1000 iron ingots per hour. Either way it should outproduce bartering even in a disfavoured conditions.
Golem based iron farms (Based on popular farm designs)
Simplistic iron farm (first link in google
https://www.youtube.com/watch?v=0L_optIDx2U) produces ...drums!..
210 iron ingots per hour... lower than a conventional strip mining for diamonds... As of an absolute min-maxing (
https://www.youtube.com/watch?v=vMSiholH_lc might be outdated as of now) it will be
3680 iron ingots per hour, though players report lower rates. Lag-wise the farm is stated to be very server friendly, probably the most lag efficeint out of the three. Typical maxed-out farms show less than
2k iron ingots per hour.
To summarize contemprorary iron farms produce about
175 to 3000 (probably less) iron ingots per hour without real player interaction.
To conclude I will say that people overestimate the efficiency of golem farms and
vastly overrate the bartering. As of now number-wise outside of fully juiced up golem-based iron farm territory the dedicated (and even not iron-targeted) mining is still the most efficent and viable way to aquire large quantities of iron. Personaly I can not imagine some personal pocket-sized golem farms will annihilate the economy, probably won't drop the framerate more than a villager trading hall. The rates of even fully maxed-out farms do not severely surpass mining. As of bartering it is nowhere near as overpowered, as some might want to present. Personally I don't see it as a viable source of iron, more of an annoyance. Farming iron from zombies is weird, but surprisingly has more potential than expected, though needs more thorough investigation.
To add up to the arguement about iron farms being unintentional and Mojang hates them. The developers litteraly asked for the feedback about iron farms during 1.14 snapshot phase (
https://www.minecraft.net/fr-fr/article ... hot-19w12a, more can be found on twitter, reddit and other weird stuff). As of right now golem-based iron farming is considered intentional and has maybe not a two-thumbs-up-approvement, but at the very least permission to exist from devs. Previously there was an issue, especially about discrepancy between bedrock and java iron golem spawning mechanics, that has been resolved in later versions of the game. By the way, despite what bedrock players actively say, java didn't really ever have any 60k iron per hour farm, while poor bedrock had less than 40 per hour - it never happened, chronics show 1.7-2 k per hour tops.
P.s. In sub-conclusions, I present all values rounded down, which reduces them by about 15 %, to have a more realistic lower bar.