Hello,
i own a 2019 250h UX, never had such a problem.
Last september i left the car parked for two weeks at the airport and when i got back it started right away.
Only thing i did for that two weeks period was to disable the keyless entry feature.
In any case i suggest you purchase a Bosch C30 charger, it's easy to use and will trickle charge the battery. It comes with a cable that can be fitted to the battery terminals, it has a connector for the cable that comes from the charger. So no worry about short circuitings when it is disconnected form the cherger.
https://www.amazon.co.uk/Bosch-Battery-Charger-Trickle-Function/dp/B0CJV44GK3?th=1