@b3m2a1 thanks very much for this! And wow, I'd never seen ResourceFunction["GithubInstall"] but it seems like I should have by now, so thanks for that too!

ArrayPlot[{{1, 1, 1, 1}, {2, 2, 2, 2}, {3, 3, 3, 3}, {4, 4, 4, 4}, {5, 5, 5, 5}}, ColorFunction -> "ThermometerColors", FrameTicks -> True, DataRange -> {All, All}]

ArrayPlot[{{1, 1, 1, 1}, {2, 2, 2, 2}, {3, 3, 3, 3}, {4, 4, 4, 4}, {5, 5, 5, 5}}, ColorFunction -> "ThermometerColors", FrameTicks -> True, DataRange -> {{1, 4}, All}]

Changing DataRange of x-axis affects the labels of the y-axis. How is this not a bug?

c.f. mathematica.stackexchange.com/questions/180901/…

Maybe one could make an (imo, poor) argument that giving an explicit {xmin, xmax} range is giving "continuous space" parameters (rather than matrix indices. i.e. you can set xmin=1.5), and such parameters should be interpreted as they are for plots, where the origin is bottom-left