Try v1 of Fusee-UF2. Thats barebones.LOL, no worries
I wonder however, if you have any plans to make a real barebones UF2, that just looks for payload.bin on the SD card root.
Barebones == no buttons combos, no strap info, no license gen, no nothing - just something that loads payload.bin if it exists and that's it.
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https://github.com/mattytrog/Fusee-UF2/blob/master/Fusee-UF2-V1_UF2/TRINKET_REBUG_FUSEE_UF2_V1.UF2