Covariant $f(Q)$ gravity is a viable extension of general relativity; however, its strong-field predictions remain largely untested. Using the static, spherically symmetric black-hole solutions of the theory, we confront it with the most stringent probes available: black-hole shadows, Event Horizon Telescope (EHT) measurements, S2-star precession, and strong gravitational lensing. We show that the two admissible solution branches behave very differently: Case I produces negligible deviations from Schwarzschild solution, whereas Case II yields significant, potentially observable corrections to the photon sphere and shadow size. From the EHT shadow diameters of M87* and Sgr A*, we obtain tight bounds, which are further strengthened by strong-lensing coefficients. These results provide the sharpest strong-field constraints on covariant $f(Q)$ gravity to date, and point toward future tests using next-generation horizon-scale imaging and precision Galactic Center astrometry.

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• Alternative gravity theories
• Classical black holes
• Cosmology