Accessing parameters of TemporalDegrain2 in Hybrid

[Selur]

What lossless format would you recommend?

Depends on the tools you use. If FFV1 is supported I would use that.

Where can I specify 10-bit encoding?

using x264, you would need to select a AVC Profile which supports 10bit and then set "x264->Base->Calculation Precision" to 10bit.

but no matter what, after closing and re-starting Hybrid the result is always the same: All path settings are blank (so the user log complains that the "Default output" path is empty)

You need to save the defaults for them to change.
reading [INFO] About profiles and saving settings,.... might help

Unfortunately, this forum software allows only uploads with a rather limited file size; is there another way to send you samples?

Post a link (or send via pm) to a GoogleDrive share or upload to MediaFire.

I can't see any problems with blocking, but which tools would you recommend?

Just to see problems of a source it often helps to enable 'Retinex'.
Depending on the blocking usually Deblock_QED is a good choice.
The denoiser should be chosen depending on the 'strength' and 'nature' of the noise. I usually try a few.
Also (assuming Vapoursynth is used) if you want only denoise the dark parts use a limitmask limitting the filtering to i.e. only luma values < 30.

Cu Selur