Can I use Oranguru's "Primate Acting" attack if I have already used a Supporter this turn?
Yes, you are not playing a second Supporter, you are just using the Supporter's effect as the effect of the attack.
Source: TPCi Rules Team (2023-01-19)

Relevant cards

Note: All applicable cards may not be listed below.
SWSH125_119
SWSH125_119