(it's out of stock directly from Polyend, but check with music stores, local and otherwise)
Just got one too and still learning about it (and really really like it). Have you seen this great video? It's a good high level tutorial of most features (it's a tiny bit dated when compared to the latest firmware, but it's still mostly the same UI)
https://www.youtube.com/watch?v=MQufJBVvAtY
Also... the Tracker supports .mod files..!
https://help.polyend.com/944600-Is-the-Tracker-able-to-impor...
And honestly the new MPCs are pretty good too, just not my preferred way of working.
That said, if there's one beef then for me it's the hard limit of 8 channels. That limit makes it very hard to do anything with chords, somewhat limiting the kinds of genres it's suitable for. Growing up with FastTracker 2, it feels a bit like a needless limitation. If my 486DX computer could do 32 channels why can't a modern piece of kit?
Even with that, though, it's a very well thought out piece of gear. I'm impressed with the software UX, they clearly spent a lot of man-hours iterating on that. Once you figure out the button combos and shortcuts it's really quite productive.
Like you though, I worry about the channel limit. While 8 channels would be plenty for sequencing monophonic parts, as soon as you start throwing chords in there, or even just mono parts where you want the notes to overlap and decay naturally, 8 channels seems a drastic limitation. The hardware in there must surely be able to handle 32 channels? An internal battery would also have been a useful feature.