Does DactNix Arch Linux support my use case?

[diederik]

Video decoding is probably not working very well and not in all applications (https://wiki.pine64.org/wiki/Quartz64_De...ing_Status).

For both VLC and MPV it would only use CPU based decoding. Both use ffmpeg and VLC hasn't even transitioned to ffmpeg 5 and from that Upstreaming Status page you can see that there's not much progress wrt Hardware based decoding ... for 2.5 years now.

I see on that page it says
Video Decode  GStreamer only, no ffmpeg [7]

So if both VLC and MPV use ffmpeg, then they won't work?

They won't use hardware acceleration, hence my earlier remark that the CPU would have to do all the work.

Also on that same page it says

Current Status
Working
...

What that table (mostly) talks about is whether there is support for it in the kernel.

But for some, like video, you also need to have support in 'userland'.
The userland ffmpeg tools do NOT take advantage of the hardware acceleration features available in the kernel.
But apparently gstreamer does, but I have (almost) no experience with it.

I am interested in the Video Encode, Video Decode, and Audio sections.
Can you explain what these terms are, what does this mean?

I didn't post it earlier as @fxc already said it, but if it helps I can '+1' their statement:
this device is (currently) not for you.

That applies for everyone who would need to look up those terms.

My tablet doesn't need WiFi, Bluetooth, or working cameras. In fact, I consider that a plus. Because I want to use my tablet as just a screen that I can carry around. I don't want it to have any wireless connectivity capabilities, I don't want it to connect with the cloud, and I don't want it be spying on me.

These are not Android devices where you get spying-all-the-time 'for free'.
(Actual) Linux programs (and their developers) tend to be quite pro privacy, so your presumption is incorrect.