The observational support for luminiferous ether and Planet Vulcan was also quite strong until suddenly it wasn't.
Was it?
So, your list of the experiments which supported the existence of the luminiferous æther before (say) 1894 starts with (please supply details) and ends with (please supply details.
"Everybody" thought that Maxwell's electromagnetic equations implied the presence of some sort of "luminiferous" ("light generating") æther in which the vibrations of Maxwell's theory took place and propagated. But AIUI, the first two attempts to actually measure it's properties (Lorentz - of the infamous contraction expression - measuring the speed of light ; then Michelson & Morley's attempt to measure the difference in speed of light between directions) in the late 1880s and mid-1890s respectively failed to detect it's properties ... throwing a large spanner into the cogs of late 19th Century physics.
Which is exactly how the modern secular Patron Saint of Physics, Feynman, would want it to work. Paraphrasing, "no matter how beautiful your theory, if it disagrees with experiment, it's wrong."
Planet Vulcan was another idea lots of people had, but nobody could demonstrate by those pesky experiments. People kept on trying to repeat LeVerrier's successful (but probably coincidental prediction of the orbit of Neptune ... and their experiments failed at the "measure stage of the "model, predict, measure, compare, revise model" cycle of the scientific method. Again, the Patron Saint of Physics would smile benevolently and tell people to not be so attached to their hypotheses, no matter how beautiful.
Nobody has observed dark matter
No, but multiple people have tried to get models of the distribution of "bright" matter and the observed radial velocities of matter in many places to align, and they can't get them to agree. Which means that either our theory of gravity is wrong (which attracts around 50 papers /month on ArXiv, the last time I took the numbers ; dark matter by contrast, gets about 3000/ month ; data and methods at wellsite-geologist.blogspot.com/2024/01/2023-01-04-first-new-shorter-post-state.html) or our theories of how galaxies turn non-luminous, boring baryonic matter into "bright" objects are all wrong (there are many and none of them give a gravity-consistent answer). Or the hypothesis that the distribution of "brightness" is closely correlated with the distribution of gravitating material. And that latter means either "dark" gravitating matter, or bright non-gravitating matter.
Outside the occasional "Electric Universe" wingnuts, I've not heard of anyone seriously proposing bright, gravity-free (or gravity-low) matter. Which ideas are you familiar with - I should add those theories keywords to my literature probes.
we have no idea what it [dark matter] is, and all the evidence is circumstantial.
Which puts us in a comparable position to late 19th century physicists after Lorentz and Michelson-Morley blew holes below the waterline of the "Luminiferous Ãther" : we know things don't add up, and we're (scientists in general) are trying to find an answer consistent with all our data. But ... no clear answer yet.
I wonder if the "dark matter" problem will turn out to be related to the "general relativity is not quantised, but QM is, and they're both right to 10+ significant digits" problem. It would be nice if they're aspects of the same problem. But I wouldn't put more than one beer voucher on the bet.
If our position today is comparable to the 1890s (with a much more active peanut gallery), then we'd be optimistic to hope for a solution much this side of 2050. I'd be pleasantly surprised to see a (confirmed) solution in my lifetime.