mixing becomes mɪksɪn what name is this process?

sounds like

loving

lʌvɪn

fucking

fʌkɪn

something

sʌmθɪn

resting

restɪn

mixing

mɪksɪn

what do we call this process?

I read here that it's more than a phonological process. (If you want to read it, note that they're using the SAMPA, not the IPA, where N stands for ŋ.)

I'm still looking for the name and more details.

I've found this and am looking no more. Thanks for your great question, I've learnt something new.

velar nasal to alveolar nasal is acceptable in some dialects.