From May 26 to June 1, the mobile communication measurement week Mobilfunk-Messwoche) takes place in Germany. Smartphone users are asked to check their network coverage with an App from Bundesnetzagentur.
Prof. Kellerer in interview by SAT.1 Bayern (26.5.2025, 17:30): https://www.sat1.de/serien/1730-sat1-bayern/videos/funkloecher-per-app-melden-was-bringt-das-fuer-bayerns-netzausbau-v_z1t65now7r31
More on the measurement campaign: https://check-dein-netz.de/en/