I could use a nudge to to understand how to get VFD working on Tanix TX6. I understood openvfd is not an option for LE anymore.
I suggest that you take a look at this snippet:
and read following conversation:
https://oftc.irclog.whitequark.org/linux-sunxi/2021-06-16#30012323 and maybe check openvfd code for FD650 commands (chip used in Tanix TX6). Note, above example was never tested in LE. I don't know if above libs are included, most probably not. Last but not least, it's not completely standard I2C communication. For each transmission you have to set "Ignore ACK" or similar flag.
Randomly at reboot (the very first one after resize for instance)
I hoped nobody will experience that. I got such issues when RSB bus was clocked at 4 MHz. I lowered that to 100 kHz and never observed such issue again. I guess I could lower it still. I'll prepare test dtb file, which you can just replace on SD card for testing purposes.
Analog audio output not available.
It's stated in OP that H6 image doesn't support analogue audio. Driver is missing. I wrote one, but due to configuration issues, I never PRed it. I guess it's LE12 material.
Just for my understanding, if the WiFi chip get supported in the mainline Linux kernel in the future, should it be supported by LE?
Yes, but chances for that are low.