I've been using this for a while, but recently I've started seeing "reuse.project - WARNING - could not find supported VCS" at the top of my results, then it completely fails to use the gitignore (as you'd expect). Sample is here: https://github.com/rpavlik/PrettyRegistryXml/runs/7679546043?check_suite_focus=true with commit rpavlik/PrettyRegistryXml@142e987 (trying to fix it)

if I put the REUSE check before I make any gitignored artifacts, it works once again, but this definitely used to work in the past.