Hi folks,
it works! thanks all. Here are the course of events:
1) tried waitusb=5 .. did not help;
2) checked permissions again, seemed fine.. last resort (since I think this is auto), chowned /mnt/sde1 itself. Works! I can only assume it inherits the ownership of the root folder of the partition? (say . at /)
3) went on to follow the instructions to load a tce dir from a raid setup (made from another distro and works with it). Went mostly without hiccups;
4) boot then can't find sde1, which this time was solved by waitusb=1 ...
So original problem is solved. (thanks!)
new problem is it cannot find the mdadm partition. It loads the tailor made mdadm-boot.tcz (so the usb is fine indeed, although I'd like to know of where to buy something that actually respects the lock.. my SD adaptors to microSD (or is the other way around?) make no difference when "locked")
the packages for mdadm, raid and squashfs, along with some others for wifi (for when I tried to get them from the CLI unsuccessfully) are still there. (on /pre, in the usb, together with the mdadm-boot.tcz above, which loads)
If I try to add mdadm.tcz to onboot.lst it shows some complaint messages which I can't read (any way to pause that boot screen?).
There are a couple of those messages that seem to always appear(even with only mdadm-boot.tcz on the onboot.lst):
A mkdir one (I think it's on tce/optional? but says it can't find it, could just be mdadm is not loading the raid), and below that a chown one (possibly on the same dir)
Another symptom: when I was building the package and working with mdadm, it found the raid and all but the partition was empty. (no tce dir or anything else). Perhaps the filesystem mounting is happening before it and a onboot command should be added (perhaps a etc/fstab?)