Those third party Web browsers maybe out of date and no longer secure to use ,since your iOS 12 iPad is, at least almost 10-years old, now.
These iOS 12 version Web browsers may not have had any updatea in quite some time.
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.
So, it is, now, past year three and third party app support has been on a quick and steady, downward/decline trend for all iOS 12 supported devices.
Many popular 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.
Look for many more third party apps dropping support for all iOS 12 supported devices as the 2023 year progresses to its end.
The immediately above statement is what you really need to worry about.
In addition, all of the various iOS 12 Web browsers, that were once available for these older iPad models, should still be safe to use for a while longer, you can still use that iPad the way it has always been used, but know that 9 to 10-year old iPad models will no longer have access to any current apps.
That older Safari Web browser may, or may not, be too old old and no longer secure to access certain types of Website, as well.
Compatible third party Web browsers for over 8-11 year old iPad models are few, now.
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.
These are the ONLY iOS 9 and later compatible Web browsers left for very old iPad models.
Plus, no way to know when Apple will cut off all security support for these nearly 9 and 10-year old devices.
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 2023, now.
iPadOS 16.5 is here. Soon to come iPadOS 17.
These nearly 9 to 10-year old, iOS 12 iPad models are coming to the full end of their support life.
These iPad models will be 4 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 2015 and later.
All of these older model iPads below CAN, currently, run the latest releases of iPadOS 16 AND the up and coming 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 )
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 )
2017, 9.7 inch screen iPad 5th gen models ( NO Pencil support ) (up and coming iPadOS 17 NOT supported )
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!