This is makeindex, version 2.16 [TeX Live 2022] (kpathsea + Thai support).
Scanning input file scyther-manual.idx....done (122 entries accepted, 0 rejected).
Sorting entries....done (900 comparisons).
Generating output file scyther-manual.ind....done (181 lines written, 0 warnings).
Output written in scyther-manual.ind.
Transcript written in scyther-manual.ilg.