Cross-posted from Degoogle, this is my update from the original post looking for hardware advice, now I need some software advice.

I got my mitts on a used Raspberry Pi 4, I installed Lineage OS on the lil guy to do an Android TV thing (via Konstakangs build.)

However, while I had success getting the OS on there, after many dumb little issues that I caused through ignorance or accident, the guides I followed for installation all focus on putting Google apps on there. (I hope to avoid Google altogether)

This is the guide I used the most.

Now I am a little stuck on my next step.
The only apps I have on the box are settings and a file manager.

How can I get, say, the Aurora app store or AFTVnews downloader on the device?
Goal being, I want 2 apps, Plex and Smarttube.

I use lineage on my phone and tablet and that's easy as they have browsers and I can alternately do it through ADB on my Laptop.

One can get the APKs for these, but I have no idea how to apply them to the Raspberry Pi.

Other future issues are, a usable remote (I have an old amazon firestick remote) and the screen is a little cut off at the edges, my tv is so old it doesn't have any overscan options in settings.
Plugging the laptop (Linux Mint) into an HDMI to the TV does this also.
Didn't do that when I used Windows so that's a tomorrow problem I guess.

UPDATE 1:

Well, that was easier than I thought!
Turns out ADB can connect to your pi via the simple method of finding the IP address of your Android TV
(Settings - System - Network)
Then on your PC in the terminal, run adb connect
And you can install your APKs from there.
This guide has all the details.

UPDATE 2:

Ok, fixed the Overscan issue on my 20 year old Sony Bravia.
In system settings (OS, not TV) I set the resolution to 1360x768 rather than 1920x1080 and rebooted.
ALWAYS reboot after changing something, didn't think I needed to, but yes, yes I do.

Next step, Remote control...

Ok, that's really cool; thanks for sharing! Speaking from the Nvidia Shield perspective, I solved the lineage lack of app store by side-loading fdroid (later replaced by Flicky, fdroid client with a friendlier TV UI).

Once you have a working fdroid client you can basically solve anything. With fdroid I was able to add KDE Connect, enabling me to sideload additional apps directly from my phone.

I updated the main post with the solution!
I have my 2 little apps and paired a pro controller and now it all seems to be working!