The IT format has a resonant lowpass filter, so that is already possible in IT/Schism (with some trickery you can turn it into a highpass filter too).
Note that the Amiga filter Steffest talks about has no parameters, i.e. it is either on or off, but you cannot configure the cutoff frequency (since that's not what it was meant to be used for).
A delay can be achieved by pasting the same channel data into another channel but with a slight... delay.
This is easiest in IT format where you can set the channel volume for this echo channel to e.g. 30% and hence do not have to adjust all volume commands manually.
For creating reverbs and other DSP effects, I would recommand loading a reverb plugin into a modern tracker like OpenMPT (or any other DAW) and "bake" the reverb into the sample data. Back in the days, people would have used early software reverbs or the well-established hardware reverb processing units for this.