Apparently they're using a simple 4g/3g/2g modem with Russian SIM, which is the reason why all russian ISPs completely turn off mobile internet (& voice) when drone launches are detected (clearly hasn't helped here as the drones were launched from trucks super close to the targets).

These launches specifically seem to have also used on-board AI targeting models trained on photos of the plane models to hit, I assume as a fallback in case mobile connection isn't available inside the bases (and photos on some Telegram channels seem to show usage of the FOSS autopilot system ArduPilot (https://ardupilot.org))