I use the Octatrack. If you don’t have of patience to learn the master of all hardware sampler/loopers, I don’t suggest you buy one. As well as what Max Marco summarizes in this video: https://youtu.be/2LrnBz0TpPY
After all that, if you still want to capture perfect loops of your synths controlled by the squarp, the octatrack will do amazing things. I’ve been using a foot pedal to capture loops, using the very hidden menu of Quantize Recording and Quantize playback. The squarp will March along with the octatrack, and I set the recording trigger to quantize at “pattern length,” which can be any 1/16th note/step length up to 64. The coolest part, is that if you start a pattern on the squarp that is longer than 64 steps, the “pickup machine” track type in the octatrack will recognize and auto snap the recordings from 64 to 128, then to 256, then the 512 STEPS! You can watch the steps counter go up that high, along with the steps in your squarp track length display page. This is the intuitive way to capture improvised ideas, in case you were maybe wanting the hand automate synth parameters beyond the length of the squarp pattern, yet have the sampler (octatrack) keep recording beyond the squarp’s pattern length, yet not need to worry about taking you hands off the synth once 128/256/512 comes around… just tap the foot pedal “Rec” button and when that octatrack pattern comes to its end (I use 1 or 4 pages of 16 steps, for uniformity), it will auto stop recording and start playing back the loop.