Your iPad year and model is too old.
The 2013 iPad Air 1 ( “A” model number A1474/1475/1476 ), iPad Mini 2 ( “ A” model number A1489/1490/1491 ) and the 2014 iPad Mini 3 ( “A” model number A1599/1600/1601 ) cannot upgrade beyond any version of iOS 12.
These iPad models have overall internal hardware that is too old, too underpowered and incapable of running all of the new, advanced and internal hardware resource intensive features of the newest iPadOS versions.
These iPad models are 9 and 10-years old, now, in 2023.
Sorry.
Third party app support, typically, continues for 2-3 years AFTER Apple ends full support of a subset of their devices.
The last major update to iOS 12 was in 2019, with iOS 12.3.
Apple has stopped issuing any major iOS 12 updates for these very old iPad models and have been ONLY issuing security, “point” updates for the past few years.
It is well past the three year mark and third party app iOS 12 support/compatibility has been on a quick and steady, downward/decline trend for all iOS 12 supported devices.
Many third party apps are no longer available to 9 to 10-year old iPad models that are, permanently, stuck at some version of iOS 12, or earlier iOS version.
That older Safari Web browser may, or may not, be too old old to access certain types of Website, as well.
Compatible third party Web browsers for over 9-10 year and older iPad models are nearly non-existent.
Here are few third party Web browsers left, to look at, in the iOS App Store, that are still getting regular updates and are still compatible with your iOS 12 iPad year and model.
Alook Web browser
iCab mobile Web browser
Opera Web browser.
Also, the internal, rechargeable batteries in these old iPads are, also, running on borrowed time.
Not worth the costs to replace these old internal, rechargeable batteries in these old iPads, any longer, either.
Also, these very old iPad models have NO real trade-in nor any resale value, either.
Sorry.
You need to consider that it is nearing the end of 2023.
iPadOS 17 is here!
These 9-years old, and older, iPad models are pretty much at their end of life and are obsolete!
Third party app support is almost non-existent, now, in 2023.
These iPad models are, at the very least, five OS iterations behind, now!
You really need to seriously consider a purchase of a new iPad model OR a much, MUCH “newer” and less expensive, refurbished or used iPad models, from better known, trusted sources, like other Apple product/device retailers/resellers, some locally or from online, on the Web/Internet, capable of running the latest iPadOS versions.
There are PLENTY of newer, older iPad models that can run the latest, current versions of iPadOS.
If you need OR ONLY able to afford to purchase older, less expensive iPad models, look at older IPads from 2017 and later.
All of these older model iPads below CAN, currently, run the latest releases of iPadOS 17.
2017, 12.9 inch screen iPad Pro models ( 1st gen Pencil support )
2017, 10.5 inch screen iPad Pro models ( 1st gen Pencil support )
( The above iPad models, probably, are at their last full year of full Apple OS support. )
2018 11 inch or 12.9 inch screen iPad Pro models ( 2nd gen Pencil support )
2020 11 inch or 12.9 inch screen iPad Pro models ( 2nd gen Pencil support )
2018, 9.7 inch screen iPad 6th gen models ( 1st gen Pencil support )
2019, 10.2 inch screen iPad 7th gen models ( 1st gen Pencil support )
2020, 10.2 inch screen iPad 8th gen models ( 1st gen Pencil support )
2020, 10.2 inch screen iPad 8th gen models ( 1st gen Pencil support )
2021, 10.2 inch screen iPad 9th gen models ( 1st gen Pencil support )
2018, 11 inch or 12.9 inch screen iPad Pro models ( 2nd gen Pencil support )
2019, 10.5 inch screen iPad Air 3rd gen models ( 1st gen Pencil support )
2021 10.9 inch screen iPad Air 4th gen models ( 2nd gen Pencil support )
2019, 7.9 inch screen iPad Mini 5th gen models ( 1st gen Pencil support )
2021 8.3 inch screen iPad Mini 6th gen models ( 2nd gen Pencil support )
Get the largest internal data storage model you can afford as NO Apple iOS device has ANY expandable storage.
I am sorry that you had to learn all of this, but this does not change any of the facts regarding these old iOS devices.
Sorry & Best of Luck to You!