Got it working on two bench units and one in the field. I used the upper half of flash plus a 16 KB bootloader. First try failed because I set fw_title on the package to “irr_stm32” and the ESP32 checked for a dash, so it just sat in Queued. Named it properly and it went through to UPDATED with the new current_fw_version.
Timestamps in UTC or it didn't happen.