I finally got frustrated with the state of the firmware for the Enviro series, especially when running on USB power, so I wrote a configuration for ESPHome for it instead. You can find it here: ESPHome on the Pimoroni Enviro Weather · GitHub
The board now runs fine for weeks and weeks whereas before it hung regularly, and I get all the measurements I want in my Home Assistant for further usage:
(yes, they look weird because the station is indoors at the moment)