For LE installation in that case enough 1-2GB space... a 128GB or bigger SSD isn't a waste for this? The gain? 1-2 seconds of booting time? When comparing with the SSD, I talking about a good SD card like a Samsung EVO Plus or Kingston Canvas Go Plus. To repeat myself: But this is only my point of view...
As mentioned in the first post, it is a spare nvme which i tried in my nas as a cache, but in my use case it does not make any difference. And as that nvme only had cost me 20€ a few months ago (otherwise i had not tried that cache thing at all) and was effectively cheaper as a 64GB sd card....and who knows what i need to store additionally direct on disc.
Main Part of post:
Got the install on the nvme working over the weekend, but it was not that fast and easy as hoped.
First i had to format the nvme and put it in the external enclosure (was lucky that the pad on the inserted nvme did not sat at the case, so i could take it out and back in without problems), as neither the pi, or windows could see the file system used by synology.
At the same time i put the image with the imager onto it, back into the pi and booted with the sd card to see if it gets seen which was the case.
Booted without the sd card, got into the pi menu thing (aka, nvme apparently was not seen as boot medium).
Tried the imager way with that....which did not work as the download of it kept staying at 0%....no idea why, as the lan connection worked.
Tried to change the boot order (saw that i could choose nvme there too) but it always fell back to network boot (or something like that) which failed.
Saw this thread with this post before RE: fresh install on nvme ssd did that (only the part with inserting the boot order) and i got my fresh install, and could load the backup file into the system.