Help How to revive old 500mb ram tablet ?

The trouble with custom firmware is that that has to be built for the specific model. So with an old, obscure device that's much less likely to exist.

The "random non-deletable" apps can just be disabled. That way they won't be able to run, and so won't cause you any problems. You'd not gain storage space by removing them as they live in the ROM anyway. That's probably the one concrete suggestion I can make, unfortunately.

Garbage can it

It's not just a software issue with such a dated tablet, there are unavoidable hardware limitations. Use it as is and readjust your expectations, or just avoid all the frustration and get a new or at least newer tablet.

What you need to do, if you really want to use it, is to use a small, fast browser to watch Youtube.

You mentioned light browsing anyway.

Save Youtube as a bookmark, so that it is right at your fingertips.

If you don't want to have to log in each time, don't set it to erase cookies.

The next step is to go into the app settings and disable any bloatware that you can.

This won't increase the useable memory, but it will free up some RAM if those apps run a lot.
Androids of that era didn't manage apps as well as modern OS.

So, if it has Amazon as an app, and it runs constantly, then it is better to disable it.

You can always use the browser to get to Amazon.

This works for Facebook, Gab, and many other apps that also have websites.

The browser that I normally recommend will likely work on that OS. If not, scroll through the different versions available until you find one compatible with your device. The lowest OS that it will run on is listed in the description.

If needed, you can download it with a different device, then transfer it via bluetooth or other method to the old device.

When you try to install it, there will be 'end of the world' warnings.

I have used this browser for years, and my phones have never self destructed, lol, so follow the instructions and install it.

Stay away from Chrome (disable if possible) or any other bloated browser.

You are attempting to use a very limited device by today's standards, and you are trying to use it on today's internet.

https://f-droid.org/en/packages/acr.browser.lightning/

If you like it, and want it to be a bit more secure and easy on the eyes, there are many settings available.

The built in ad-blocker is a nice touch.

Also, I am available to answer questions about it.