My first step would be to look if they are supported by Linux. Many tablets aren't.

From what I can find it has a quad-core Cortex-A7 ARM32 chip, a.k.a Mediatek MT8321, with 1 GB of RAM and 8 GB of storage, which is not plenty for a device running Android 8.

Your best bet for running "Linux OS" is postmarketOS. But the ARM world is a lot different than the x86 world that you might be familiar with: you can't just "install" any OS on an ARM platform, you need to port it (write code & tweak config) for each device. And the only device that has the same SoC does not look good.

So you next best choice is probably Termux. It could be installed on any Android devices, and provides a decent "Linux" environment that are pretty close to a real Linux console. Of course, it's really difficult to run GUI applications, and running things like Docker would probably be out of the questions (ARM32 already had pretty rough Docker support as-is). But still, it's a good way to get your hands dirty with Linux, and you can definitely use them for quite a few things: writing C or Python code on the go, get familiar with command line, or just run a few small services (e.g. SSH for remote connection, NginX for web server). The possibilities are still endless.

Now, as for the de-googling part, you will still need a custom ROM for this, and I'm not even sure if your device even support flashing third-party ROMs (some carriers would lock it down), so it might not be possible to flash an entire new OS, but someone else seemed to have already posted a potential ROM you could try. Still, you can still find some tutorials that can help you disable as much Google as possible with ADB command, which you might need to adapt to your specific device.

If you can get this working

https://www.needrom.com/download/alcatel-1t-7-9009g/

You might have luck installing an arm linux on it.

PostmarketOS might be a possibility…

Lmk if you manage to get it to work

Try Manjaro's KDE mobile.