Are there any non-butterworth implementations of Linkwitz-Riley Crossover arrangement?

Answer 1

It depends on how you look at it; the Butterworth filter is probably the only filter with absolutely flat response in the passband, and the knees/slopes of the filters of the Butterworth filters add upp more or less perfectly at the crossover (for example in a loudspeaker filter).

The Linkwitz-Riley is built up through putting two filters in cascade, and it has an absolutely flat passband. As soon as you find a filter that can be arranged in cascade and that has an absolutely flat passband; you're there!

And when/if you're "there", you will probably come to the conclusion that the filter you found turned out to be a Butterworth... =/

Some might yell out: "what about ChebyshevII?" Well, that one does not have that smooth knee of the Butterworth, and it has the stopband ripple that has to be taken into account.

Here's an idea: Throw together two Chebyshevs in cascade (series) and find a good motivation to why it's a good filter, and you can name it after yourself. Sick but true!