My wife wants an alternative to the heavy Hörmann HS4-868 BS BLACK, which suffers from bad battery contacts.

The Hörmann HSE 1-868-BS would be a great alternative if it had been available and at a reasonable price <€20.

So it looks like we'll have to make something ourselves:

• SoC
  • ESP8266 : ESP-WROOM-02D-N2
  • ESP32-S2 (with onboard USB) : ESP32-S2-SOLO-N4 (NRND), the ESP32-S2 WROOM module would be a better choice (when it becomes available)
• LIR2450 cell
• a battery holder : Keystone 3009
• a button
• a bicolor LED
• optional : micro-usb connector + charging circuitry

Development could be done using Adafruit's TinyS2.  It has almost everything already on board.  It also allows for development in Circuitpython.