Daily briefing
ExpressLRS 4.x introduced a major compatibility break with 3.x-era transmitters and receivers. Current project documentation continues to emphasize broad 2.4 GHz, 900 MHz and dual-band hardware support, while community upgrade guidance warns that transmitter and receiver major versions must match.
RC link upgrades can strand aircraft when a pilot updates the radio module but forgets receivers across the fleet.
Inventory receiver versions first, then upgrade TX and RX as a planned fleet migration. Keep a known-good configuration for aircraft that cannot move to the new major version.