Student in IT with a digital forensics degree but, “that could be said with any software you install.” That’s not how security works you shouldn’t think about, “am I vulnerable because all software and hardware is vulnerable.” You should consider it like, “how likely am I at risk of being hacked with this software/hardware.” What is the trust worthiness.
Like consider this would you buy a gun from a stranger or from an official source. Which is likely to get you on a radar for a stolen weapon.
I absolutely love pokemon and I mean that with passion. I have an original, Gameboy, Gameboy SP, Nintendo DS, and 3DS with all of their corresponding Pokemon games, Crystal, Fire red, Leaf green, ruby, etc like genuinely love the game but I am absolutely wary of anything that runs well on iOS or Android unless I know where it is coming from.
While you might be fine what you should be aware of is that iOS doesn’t just always allow this kind of thing.
Additionally, compiling your own code from GitHub also doesn’t mean anything. Open Source is great but the chances of malware being less of a thing aren’t exactly true. I hope you enjoy the game but when their are actual security experts (I am not including myself in that category) telling you to be wary. I would consider those statements.