I found this post from @dave about implementing reverb but despite the date of January '23 I did not see mention of it elsewhere in the forum or in the Lua SDK docs. Is this slated for any upcoming release? It would be nice to have a configurable implementation of this effect to use dynamically rather than bake it into samples etc.
Here's a demo!
reverb.zip (176.6 KB)
It takes about 50% of the CPU as is. Surprisingly, converting it from floating point to fixed point doesn't speed it up at all, even with being able to use some Cortex-M DSP functions that way. 
You could reduce the number of delays to gain speed at the expense of quality.
Oh interesting, thanks for sharing! I'll try to take a closer look at it over the weekend.