If you mean a pi alternative as in a single board computer with an ARM processor then probably the RockPro64. This is what powers my Tanto Ronin Dojo node but it should work fine, if not better than a pi, for a LN node.
Pierre Rochard made Node Launcher for Lightning Node on Desktop. But unfortunately the project han't been updated in a long time. I hope it get's picked up again one day because I thought it was really cool.
Not sure whether this would work but I'd be very interested to see if it could be done. I think the continual writing on to the SD, and db size will become a problem.
Even if the storage and other other specs seemed similar to a Pi, the difficulty to maintain regular upgrades, installing and uninstalling various tools.
If the question is for running a node in a fairly serious attempt to either route payments not just for your own payments, you'd need to maintain a synced blockchain, and keep synced to the lightning graph as much as possible.
I'd go with one of the other small form-factor cpus, nuc, laptop or desktop.
Laptops work well for me.