Just converted some dusty Perl script to Python, and fixed it a little.
The fmt command from GNU coreutils still struggles with utf8, and you are, like me, working with plain text files with non-ASCII character sets, chances are it won’t format them correctly.
Here is the link (tell me if it’s visible):
https://gitlab.com/fauve.ua/text-tools/-/blob/main/adj?ref_type=heads
Place it in your PATH (mine is ~/.run), and execute adj -h.
Often using it from within Vim (by highlighting text with v, and running : adj -f -w 80 or something like that).