I've misunderstood the FS limits, 255 is for filename, not path.
Path is limited only by libc, it's 4096.
The default outtmpl in musicdlp contains slashes, so it's a path.
But YDL considers it to be a filename, so the whole
outtmpl formatting result is trimmed to path_length.
Do we really need this? I think there are no "malicious" long-named tracks :)