See if this commit works for playback ffmpeg: use JC branch (at working commit) for testing · chewitt/LibreELEC.tv@4325503 · GitHub (will need you to build your own image).
Backup only supports local storage. If you want to write to a remote share, setup a systemd kernel mount to locally mount the remote share, then write the backup to the "local" folder.
I think jernej has something in his Allwinner images for flashing things to emmc, but "emmctool" only exists in my Amlogic images; hence you cannot find it to use.
cd /storage
wget https://chewitt.libreelec.tv/testing/LibreELEC-AMLGX.arm-10.0.0-wetek-play2.img.gz
emmctool w LibreELEC-AMLGX.arm-10.0.0-wetek-play2.img.gz^ that downloads the file, writes it to emmc, expands the storage partition, changes disk labels, then sets extlinux.conf to boot from the new disk labels (so SD boot still works).
I doubt the audience in this forum will have an opinion on Android support (not our focus). You'd be better off asking in the Radxa forum.
jock2 I'm not aware of any guides for writing wireless drivers, but I'm not sure anyone could do a worse job than the original 
The internal port might be worth trying .. I always forget about it. If not, perhaps hold the card in with a woodworking clamp (not too tight) to boot and then download/overwrite the eMMC with LibreELEC-AMLGX.arm-10.0.0-wetek-play2.img.gz. Once you flash mainline u-boot you'll be able to boot/run the LE10 image from eMMC fine (seems to work okay for me) although the current state of Amlogic in LE10 is far from perfect.
I'm not sure if the WP2 checks all USB ports or just the OTG port during boot, so experiment.
I don't include or support the community scripts for instaling stuff to emmc with vendor u-boot; my knowledge of it all is poor and the scripts often cause problems. If you boot from the "box" image you can download the "wetek-play2" image and write it to emmc (replacing vendor u-boot with mainline which I understand more) using "emmctool" .. but I'd caution against doing that unless you're comfortable with how to restore it back to the original WeTek code again should you not like it. IMHO there's not a huge difference between running from a decent SD card and eMMC.
Work has started on delinterlacing. It won't be a quick feature to add, but it will come.
Write Dropbox - bootsector.img - Simplify your life to the USB drive using any image writing tool (etcher etc.) and it will erase all partitions and allow the disk to be prepared (reimaged for LE) again. To be clear, this will nuke all content on the drive.
"devel" is the image tag for an ad-hoc built image .. not a scheduled nightly
In LE the xrandr command is only present on devices running Xorg/X11 windowing (Generic x86_64 devices) but ARM SoC devices "run on the framebuffer" with no windowing system. Other distros, e.g. Armbian are desktop focussed and will use X11. The nearest equivalent is forcing kernel DRM output modes, which can be done via boot params in extlinux.conf.
I don't have experience with SCART devices, but the standard resolution I've seen with RCA outputs (single cable) in the past is 480p/i and it's cousin the Component output (three cables) is the same but can also run at 720p and 1080p/i. Current Kodi skins are designed for a minimum 720p screen resolution but most (not all, but most) will handle 480p if needed, but lower than that I'd expect to see visual problems as none of the skin designers will be testing low resolutions. Similarly.. I doubt any of our maintainers are testing RCA/Composite output so YMMV.
Right now there's really only one developer working on Rockchip (others had to step back for personal reasons) and people have lives outside of fiddling with kernel drivers and their own sense of skillsets and where focus needs to be. There's also a lot of collaboration happening on hardware video decoders (V4L2-requests needs to work on three different SoCs we support) so it makes sense to be involved and contribute there. Meanwhile PCM audio is working and good-enough until time frees up for other things.
Those files are in the u-boot build folder (when you compile u-boot from sources).
There is nothing configurable in Kodi so you'd have to resort to some form of skin hacking to neutralise the toaster pop-up.
It depends on your knowledge/skill level. Our recommendation is still that most users do a clean install to avoid problems with add-ons which need to be replaced. If you're comfortable with the SSH console and know what files do what in Kodi, it's simple to rename the current Kodi folders out of the way, update to 10.0, then stop Kodi to migrate the important bits back into the new clean-install Kodi folders and then restart Kodi to finish the job. As a broad rule: if you don't get/understand the hints I've just dropped .. do a clean install, and if you did get them .. Good luck and off you go.
Index of /testing/ has an LE10.0.0 "box" image for WP2 (vendor u-boot) or brave souls can erase the emmc and then install mainline u-boot (to emmc) via the "wetek-play2" image but support for hardware decoding in the upstream kernel is still a bit rough and the DVB tuners are not supported. These days fewer people are shipping DVB cards in-box and my advice would be to separate "head end" with tuners that is accessed over the network from a dumb(er) "client" device. If you need the tuner and the WP2 still works; you can keep it going with current software just to serve the tuners while using a newer client device.
4K/HEVC and 1080p H264 is handled well in RPi4B, but it is missing VP9 which (along with any other codecs) is software decoded, the chip has lots of grunt though so up to 1080p that's not a big issue. Allwinner/Rockchip have continuous ongoing work around the hardware decoders but they are now quite mature and shaping up .. but there's a mix of older chips and newer ones and it's a little confusing. Amlogic (LE) has the same issues on G12/SM1 boards as the WP2/GXBB device you have (if anything they are worse, the newer chips have more complicated HEVC/VP9) but CE with legacy vendor kernels is a better option, but AFAIK they do not have DV running. OSMC does support it in their Vero 4K box, and you'll find Android devices that do it (but that's not my area of expertise).
Not sure that helps. I'm personally a fan of the RPi4B. There are lots of devices with technically better specs but it has (and will continue to have) great software support and IMHO that's the most important thing for longegivity of devices.
v6.8.17 was released, which resolves the issue.