Hi there,
Awesome, and thank you for contributing to the discussion.
So the UF2 are NOT what is generated when you choose (sketch) "export compiled binary " one more step after that running the converter to make the UF2’s , there is a thread on here with the exact steps required , have a LQQK 
Once you get it you want to always do it that way, drag & drop it’s in the wiki somewhere also FYI 
try also the ESP flash tool to take that binary generated and flash it straight away. (don’t over write the bootloader) or use the merged bin.
HTH
GL 
PJ 