Was testing things and ran into autofill errors with KeePassXC. Looks like the Firefox plugin manages to pass the full length of the password, even if the input field is limited to a lower number of chars. Manually pasting the password truncates it, though.
Just reread my wall of text, and I think bits and bytes are in the right places. I do have a tendency to be blind to my own typos, however, so there’s that ._.