Incompatible app download on iPad for autistic, non-verbal child

it's an old ipad mini 1g from 2012 its hardware can't run newer ios than

Last: iOS 9.3.6, released July 22, 2019 (cellular models only), otherwise iOS 9.3.5 (released August 25, 2016)

from

iPad Mini (1st generation) - Wikipedia

it's the choice of app developers which ios version they wish to support with their app so

you will have to take it up with google who make youtube and others

How to contact an app developer - Apple Support

though you would likely not get very far so

if it was me then I would look into getting him a new ipad

Regrettably, your first generation iPad mini is long ago obsolete. Your only option os to replace your iPad with a much ore recent or current model iPad.

Apple ended update support for the iPad mini1 in September 2016. Along with iPad2 and iPad3, these models of iPad cannot be updated to iOS 10 or later major versions of iOS, as the internal hardware does not meet the minimum technical requirements for newer versions of iOS/iPadOS. This limitation cannot be bypassed; these are 32-bit architecture devices, whilst all recent versions of iOS/iPadOS are designed for 64-bit hardware platforms.

You need to consider that compatible Apps for older models of iPad are no longer available - as App Developers have dropped all support for 32-bit devices. As older versions of Apps are removed from the Apple App Store, you’ll not be able to (re)download or install them - which may severely limit the usefulness and utility of your iPad. As such, if you want or need to access most current Apps, requiring more recent versions of iOS than your iPad is capable, you’ll need to consider replacement of your iPad with a newer or current model.

For information, here is a list of the highest version of iOS supported by the older models of iPad (for simplicity - “generations” are shortened to a number) that are restricted in their ability to be updated:

32-bit devices (obsolete)

iPad1 - iOS 5.1.1

iPad2, iPad3 and iPad mini1 - iOS 9.3.5 (WiFi Only models), iOS 9.3.6 (WiFi+Cellular)

iPad4 - iOS 10.3.3 (WiFi Only), iOS 10.3.4 (WiFi+Cellular)

64-bit devices

iPad Air1*, iPad mini2 and iPad mini3* - iOS 12.5.7

iPad Air2, iPad mini4 - iPadOS 15.8.4

iPad5, iPad Pro (9.7"/12.9" 1st generation)* - iPadOS 16.7.11

iPad6, iPad Pro (10.5"/12.9" 2nd generation) - iPadOS 17.7.10

(*) obsolete

Newer models are all able to be updated to the current version - iPadOS 18.6.2

• iPad Pro 13" (M4)
• iPad Pro 12.9" (3rd generation and later)
• iPad Pro 11" (1st generation and later + M4)
• iPad Air (3rd generation and later + M2/M3)
• iPad (7th generation and later)
• iPad mini (5th generation and later + A17 Pro)

That's the original iPad mini (Wi-Fi). Apple released it in October 2012. It has a 32-bit processor, can't update past iOS 9.3.5, and is thoroughly obsolete. The current iPad OS is iPadOS 18, and in just a few days, Apple will release its successor, iPadOS 26. ("26" as in "model year numbering").

I would suggest treating your son to a new iPad.

Compare iPad Models – iPad mini 2 vs. iPad mini (A17 Pro) vs. iPad (A16)

The iPad (A16) is the least expensive new model, and would give your son a larger screen than he has now. (I would have used your Pad mini 1 in the comparison, except that there wasn't an entry for it!)

If you wanted to save some money, you could look in the Certified Refurbished section of Apple's store (Refurbished iPad Deals - Apple). Apple's Certified Refurbished prices are usually only about 15% off original list. But the quality of the refurbishment is good – you get a new outer shell, a new battery, and a one-year-warranty.

Note:

• If you are thinking about buying a used iPad from any place other than Apple's Certified Refurbished store, please read The All Too Common SAD Reality of Buying a Used iPad/iPhone – Apple Community .
• Although Apple's Certified Refurbished store sells some iPads with only 64 GB of storage, I would think long and hard before getting that little. Since the iPad mini 1 came out, both iOS and apps have grown larger and hungrier for storage, and these days, 64 GB isn't very much room. (It might leave you scrambling even just to make some free space to install future iPadOS updates.)