One fix, and it is worth reflashing for.
Choosing a character did not survive a sleep
Pick Vellum, Octavo, Lumen or Sprig, put the device to sleep, and it woke up as the fox again. Every time.
The choice was being written to your SD card correctly. It was being thrown away on the way back in.
Deep sleep is a full chip reset, so settings reload from the card on every wake. That load validates each dropdown against its list of options, but the character picker builds its options as plain strings rather than translation ids, and the check only looked at the translation ids. It found none, decided every possible value was out of range, and handed back the default. Which is the fox.
It never showed up in testing because settings only reload on boot. Pick a character, use the device, and it is fine right up until the moment you close the cover.
If you picked a character in 1.0.0 or 1.0.1, you have been losing it ever since. Pick again after flashing and it will stay this time.
Nothing else was touched. Of the 31 dropdown settings in the firmware, 30 take the exact code path they always did. The character picker was the only one built in a way that tripped this.
Everything from 1.0.1 is still here
Works on all four themes, companion in the column beside the menu, OPDS servers no longer push it off screen, and no more sleep image ghosting behind the home screen.
Upgrading is just reflashing. Your streak, reading history and settings live on the SD card and are not touched.
Still only tested on an Xteink X3. Should run on an X4, but it has no RTC so streaks and the sad moods will not work. Will not boot on an X4 Pro, which is a different chip. Back up your firmware first, instructions in the README.
Found something else? Open an issue.