SN 2021adxl is a slowly evolving, luminous Type IIn supernova with asymmetric emission line profiles, similar to the well-studied SN 2010jl. We present extensive optical, near-ultraviolet, and near-infrared photometry and spectroscopy covering approximately 1.5 years after discovery. SN 2021adxl occurred in an unusual environment, atop a vigorously star-forming region that is offset from its host galaxy's core. The appearance of Lyman-alpha, OII, and the compact core would classify the host of SN 2021adxl as a Blueberry galaxy, similar to higher redshift Green Pea galaxies. Using several abundance indicators, we find the metallicity of the explosion environment to be only 10 percent of solar, the lowest reported metallicity for a Type IIn supernova environment. SN 2021adxl reaches a peak magnitude of approximately -20.2 in the r band, and since discovery, it has faded by about 4 magnitudes in the r band, with a cumulative radiated energy of approximately 1.5x10^50^erg over 18 months. SN 2021adxl shows strong signs of interaction with a complex circumstellar medium, as evidenced by the detection of X-rays, coronal emission lines, and multi-component hydrogen and helium profiles. To further understand this interaction, we model the H-alpha profile using a Monte Carlo electron scattering code. The blueshifted high-velocity component is consistent with emission from a radially thin, spherical shell, resulting in broad emission components due to electron scattering. Using the velocity evolution of this emitting shell, we find that the SN ejecta collide with circumstellar material of at least 5 solar masses, assuming a steady-state mass-loss rate of 4 to 6x10^-3^M_{sun}_/yr for the first approximately 200 days of evolution. Continued observations of SN 2021adxl may reveal signatures of dust formation or an infrared excess, similar to what was seen in SN 2010jl.