yes - uplay came back fairly quickly.
no luck with the drm-free copy (although haven't looked that hard tbh) - but found a thread where a 'Scene group' were being lauded for achieving the most thorough result in this context - and consequent testing results were contentious and contradictory (what's new?!) ...
BUT ... : DXVK, now this is interesting - and a big (if cautious, as early day/s) 'thank you' Poneros for encouraging me to give it a go.
Both games (origins and odyssey) are using the files, no question: when first in use the 'much worse' initial performance commented upon is very evident. But it does seem like the 'old days' where once things start to settle down ('building the shader pipes' is mentioned), performance is smoother. Bit like when you went to a new area in older games, turning around a few times seemed to help everything 'load'. It's actually worse than that at first - and you do need to persevere.
Sitwa in Origins is definitely better - not night and day, but noticeably smoother (and I think averages are higher) to the point where I think I could proceed rather than being discouraged by the constant and repeatable judder and stutter that the 'original' files cause.
And pretty much the same experience with Odyssey (which just looks amazing btw).
The obvious potential problem is that if you're just jogging through areas 'once', then the benefits may not acrue - and I'm not clear yet as to whether the shaders building up will cover undiscovered areas in the fullness of time. But on my one try so far, loading a save in Odyssey seemed to keep the smoothness ... which is encouraging in itself.
Having said all this I've done enough of this kind of tweaking to know that 'tomorrow' if I get out of bed the wrong side, so to speak, I could find all these positive changes gone awol ... but:
trying DXVK seems to be harmless - no files are overwritten, and if anyone's suffering the same kind of performance issues I describe in my previous posts, it might be worth giving it a go. Of course a very large YMMV.
* - should add, that as further evidence (if not necessarily of the desirable kind) that the files are indeed taking over the reins, game-specific changes in the Radeon control centre (i.e. chill frame-rate cap, 'sharpening' etc) are now being roundly ignored !
on balance I still appreciate the 'improvement' enough to persist with DXVK for the time being, and as far as I can tell freesync is still working ...
