I’m in exactly the same situation, fearing the moment when my beloved Harmony will die
I’m using
- an ESP32 as a bluetooth remote controllable through HA. See ESPHome BLE Keyboard
- cheap bluetooth and/or RF remotes that talk to HA via the “keyboard remote” integration (Keyboard Remote - Home Assistant)
- an integration of my own that simulates the “activities” of an Harmony
to “emulate” the Harmony.