It's true iOS will kill apps if they exceed memory limits, and so older devices with less RAM will experience these issues with greater frequency. It may be helpful
@Lulamay, if you can list which iPad you have (you can check this by going to Setting -> General -> About and looking for 'Model Name') and which version of iOS you're on (it will be listed on that same page).
All platforms respond to that, though. Even windows will kill an app if the RAM usage for a single program exceedes what is available. Some OSes like iOS, Nintendo's OS, etc will not swap kernel memory, or even OS (or rather, the part of the OS that's not the kernel) memory, much to the dismay of developers, but that's what makes "home menues" come back so quickly. Since we don't know for sure, i don't want to say this is the case, but usually applications use the stack for variables, unless stardew's using really large variables. Then again, i'm not 100% sure what exactly unity does, but it's just easier for everyone (especially unity devs) if stack is used. And if the stack runs out, i can't see why there couldn't be a controlled crash (then again, no one ever implements signal handlers on mobile apps, despite it being entirely possible to [though, since unity, i'm putting this more on the unity devs than ConcernedApe]).
That said, apparently crashlogs are at "~/Library/Logs/CrashReporter/MobileDevice" which i assume "~" is short for "/home/lulamay" or something like that. You can apparently extract them from itunes according to
this random page i googled, but i imagine these instructions are out of date. The "Files" app on newer iOS versions supposedly lets you browse files like you can on android platforms, which, if so, means you could navigate to this directory. I'd ask my girlfriend to show me more, but despite being so much of a fan of apple more than google, she doesn't seem to know how to navigate either fairly well (Hopefully she switches to android as soon as this pandemic ends, if our risk factors don't end up a problem). These crash logs, if you can find them, would be of great use, especially if i can find a way to read them (knowing apple, they're probably encrypted in a format that can only be read by purchasing a dev license).
I can't speak for CA, but it's worth mentioning that the mobile ports of Stardew are handled by another company, The Secret Police.