Every manufacturer has to use some way of exhaust aftertreatment on tractors above 25HP. Either DOC or DPF, they will use something.
Mahindra, most likely uses a DOC just like many manufacturers did. They claim no regens but on a DOC, it's always regening once it gets up to the required temps. That's why it's important to keep RPMs high or load the tractor so it gets the necessary exhaust temp.
Using a DPF, usually means more electronics tied into the engine, as they usually have a dosing injector before the DPF to help the regen process.
What Branson did in the new 2021 models, in order to keep the good ol'mechanically injected engines, was to use a DPF and a butterfly valve after the DPF, just like an exhaust brake on a truck. A data logger monitors the DPF and engine temps and decides when it should regen or not. If it decides to regen, it'll start closing the exhaust valve to increase the temps on the DPF.
This way, they will keep a mechanically injected engine with a standalone emissions system without having to convert to Common rail engines and all the electronics that come with it.