When will Mini 3 pro support D-LOG M? Or will it ever support it.

Thank you for your feedback. The design concept of the Mini series products is to "light and easy to shoot". Considering the balance between product performance and flight experience, relatively more professional shooting formats such as D-Log mode have not been added. We will help you to forward this suggestion to our developers, thanks for your understanding and support.

DJI Paladin Posted at 12-10 20:14
Thank you for your feedback. The design concept of the Mini series products is to "light and easy to shoot". Considering the balance between product performance and flight experience, relatively more professional shooting formats such as D-Log mode have not been added. We will help you to forward this suggestion to our developers, thanks for your understanding and support.

and why has the Mini4pro D-Log M?

It never will,  dont expect to see any new features added to the Mini 3 now the Mini 4 is out.  

DJI never adds features to drones if newer model of the same series is released. They stop working on a previous generation the moment they start working on a new one. That said, Mini 3 Pro will not receive any new features. It might receive some changes to comply with new regulations and maybe some updates to prevent some serious hacks, but that's all.

exactly,
if you want dlog-m, buy m4pro at least

UweE Posted at 12-11 08:36
and why has the Mini4pro D-Log M?

Thank you for your response. UweE. The DJI Mini 4 Pro has the advanced capability which is capable of shooting HLG and D-Log M color modes under normal video recording, MasterShots, and Quickshots. The response above is only applicable to Mini 3 Pro, Mini SE, DJI Mini 2/Mini 2 SE, and Mavic Mini. Thank you for your understanding.

Never.  The hardware simply isnt capable.  It barely manages 10 bit cinelike.

Don’t get too excited by D-LOG M. It’s not very good to work with in Davinci Resolve.You get better and more realistic results with the “Normal” 8bit REC.709 profile. And HLG colour profile. Even DJI don’t give advice on what colour space settings D-LOG M should use.
I have a Mini 4 Pro and edit my footage in Davinci Resolve

Never. Why would DJI should themselves in the foot by adding a feature that could then affect the sales of the Mini 4 Pro? Silly question!!!!