DMR

Oh, I see. This is kind of what people often do with "Cross-band" repeat modes on some mobile radios -but in your case, mixing DMR and analogue. You need to be cross-band unless you have all the filtering that is in place with an actual repeater. That MMDVM board will be overloaded unless the analogue radio is on a different band.

Yes, Allstar can absolutely be used as a repeater controller like this, but your specific plan might be easier to develop yourself from scratch, idk. Pi-star supports that MMDVM modem out of the box, but it doesn't provide a way to interface audio, and it isn't set up to do any repeater controller work. It doesn't even decode/encode audio at all, it just passes the codec data as-is.

If I was doing this, I might actually use 2 rpis -one just as a typical MMDVM/Pi-star hotspot, and another as an Allstar node connected to that analogue radio. The latter can be set up to bridge to DMR, and thus allowing your MMDVM hotspot to link in. It will need hardware or software codecs though. You might not want 2 pi settups, but that might be handy as your dmr hot spot can move around with your HT.