I was wondering whether doing Temporary Marriage is in itself a mustahabb act, seeing I’ve heard it is, but couldn’t find anything conclusive like there is for marriage in general.

We don’t have evidence that it’s mustahab in and of itself. Yes it can becomes mustahab if:

1- It protects one’s piety and guards from falling into sins.

2- If one does it once at least to reject Omar’s ban of of it and to keep the Sunnah alive if it’s being completely abandoned in society.