A hands-on debugging log covers attempts to use Ubiquiti's UniFi 5G Backup device on AT&T's network for a mobile mini-homelab project. Despite AT&T's Enterprise AIA plan and the device's certifications listing AT&T support, the U5G Backup could only connect via 4G LTE, capping speeds around 30 Mbps down. Using SSH and the mca-dump debug command, the author found the device stuck in LTE mode with 5G Standalone disabled, and AT&T rejected the device's IMEI for 5G Internet Air for Business. A separate U5G Max device with the same SIM got 500+ Mbps on AT&T's 5G network, suggesting the U5G Backup currently only fully supports 5G on T-Mobile, likely due to carrier-side approval issues with 5G RedCap rather than a hardware limitation.
Questions this post answers
Why does my Ubiquiti U5G Backup only connect at 4G LTE speeds on AT&T instead of 5G?
Even though the U5G Backup's tech specs list AT&T under certifications, AT&T currently does not authorize this specific device's IMEI for 5G on its network, causing it to fall back to 4G LTE (around 30 Mbps down, 12 Mbps up with a strong signal). Checking the debug console with the mca-dump command shows rat_mode_active as LTE and 5g_sa_mode as false, confirming no 5G Standalone connection, while the same AT&T SIM in a UniFi U5G Max reaches over 500 Mbps on 5G from the same location. Anyone troubleshooting cellular backup internet hardware can track carrier compatibility quirks like this on daily.dev.
What is the mca-dump command used for on Ubiquiti UniFi cellular devices?
Running mca-dump from the root debug console on a UniFi cellular device like the U5G Backup outputs a JSON status dump showing radio state, signal metrics, and carrier info. Useful fields include rat_mode_active (current radio access technology), 5g_sa_mode (whether 5G Standalone is active), rsrp, rsrq, rssi, and snr signal quality values, plus networkoperator and geo_info for carrier identification. Engineers debugging cellular gateways can find similar low-level diagnostic workflows on daily.dev.
How do you recover a bricked Ubiquiti U5G device stuck in an update loop?
Put the device into recovery mode and use TFTP to upload newer firmware manually, since the process shows no progress bar and can take around five minutes to transfer. This must be done over a wired connection directly attached to a switch; attempting it over Wi-Fi, even with a strong signal, can cause TFTP transfers to fail with corrupted bytes. Those recovering bricked network hardware can compare firmware troubleshooting notes on daily.dev.