midifilter.lv2 VS OpenDeck

You can use the MIDI Key-Range Filter (by Robin Gareus) https://x42-plugins.com/x42/x42-midifilter . Add an Ardour midi bus. Use Ardour to change the output of your piano to the new midi bus. Add 2 plugins to the midi bus 1) an instance of the Midi Key-Range Filter, 2) copy your piano midi instrument to the midi bus. Left click on the Midi Key-Range Filter, set the low and high note to E4, set the operation range to "Exclude Range". You are instructing the Midi Key Range Filter to output all notes except #E4.

And don't forget about midi humanization/randomization plugins, though, like X42 ones, so it won't sound dull or robotic.

i'd suggest using one of R Gareus lv2filters (https://x42-plugins.com/x42/x42-midifilter) possibly hosted by the jalv program if there is no other LV2 host in your setup. The "midi keys transpose filter" might do what you want. It might be agood starting point if you need to roll your own.

I am not specialist by complex MIDI work, but as I know there are MIDI filters. So you can route the same Musescore MIDI output to some MIDI tracks in Ardour and filter out all except of required instrument for each Ardour track. May be MIDI Channel filter will do this work: https://x42-plugins.com/x42/x42-midifilter

Not sure if FLStudio supports LV2 plugins, but there might be something here: https://x42-plugins.com/x42/x42-midifilter

Does qsampler support lv2.plugins or can you run it in a plugin host? https://github.com/x42/midifilter.lv2 has a plugins to filter on a variety of criteria, I'd be surprised if it can filter pitch-bends.

There are lots of projects, my fav - https://github.com/shanteacontrols/OpenDeck

DIY might be the way to go - this is one option https://shanteacontrols.com/

Checkout OpenDeck. Github repo here. It supports lots of different boards and no programming is required at all. I've used it for everything from 8 channel consoles for my DAW to a full-featured live controller for AmpliTube.