GA pilot reported descending below minimum altitude during approach and receiving a low altitude alert from ATC. Pilot continued to landing.

Narrative

During an IPC; I was performing the ILS Runway XX approach into ZZZ. The VHF NAV radio was properly selected and identified. I was established inbound on the localizer; and the glideslope was intercepted at ZZZZZ INT. While inbound to ZZZZZ1 INT and descending on the glideslope; I observed fluctuations in the glideslope indications. However; no NAV flags were displayed on the unit to indicate a loss of signal.Due to the distraction caused by troubleshooting the fluctuating glideslope; the aircraft descended below the published minimum altitude of 1660 feet prior to reaching the final approach fix at ZZZZZ1. At this time; visual meteorological conditions (VMC) prevailed; and ZZZ Tower alerted us of our low altitude. Upon receiving the advisory; we transitioned to a visual approach and proceeded to land safely at the airport.I was using the Garmin Pilot application on an iPad as an electronic flight display (EFD) to view the approach chart. However; due to the older generation of my iPad; I was unable to use Garmin's Smart Airway Chart feature. This feature displays own-ship position on both the plan-view and profile-view of the approach plate. If this capability had been available; it likely would have alerted me to the deviation from the correct glideslope path more promptly.Lessons Learned:Ensure that electronic devices used as EFBs or EFDs are updated and capable of supporting all available situational awareness features; especially for IFR operations.In the presence of any anomalies with navigational equipment--particularly during critical phases of flight--immediate adherence to minimum altitudes and backup verification methods (such as cross-checking raw data or switching NAV sources) is essential.Maintain situational awareness and be prepared to revert to a visual approach when conditions permit; particularly if navigation guidance becomes unreliable.