Hi,
just a brief report that I was able to integrate a Diehl Hydrus 2.0 watermeter into Home Assistant with cheap hardware and ESPHome. If you're looking to do the same, check out the link below.
The hardware: a ESP32-C6 Super Mini and a CC1101 868MHz module (and some wires and a USB charger + cable), less than 15 Euros in total. I preferred that over spending 50-80 Euros on a wmBus USB stick 
Only catch is getting the meter's encryption key from the water provider - but thankfully my provider was helpful.
Here's the tutorial that I followed, with the necessary ESPHome config: GitHub - red-black-bonsai/howto-hydrus2-smarthome: HowTo for adding a Diehl Hydrus 2.0 water meter to a smart home using ESPHome and SzczepanLeon's wmbus esphome modules. · GitHub
Kudos to SzczepanLeon for creating the ESPHome module used in the config!