It seems that cryptswap is working correctly on 17.10 with the kernel 4.13.0-36-generic on a different machine using the same test as described above. I tried the same kernel (4.13.0-36) on 18.04 (machine used in original post) and it still fails. Of course, I checked that the swap appears in /proc/meminfo. Hope this provides a clue.
[FYI, I'm using 4.13.0-36 rather than 4.13.0-38 because of a bad firmware interaction with 4.13.0-37 and 4.13.0-38 that results in CPU lockups]
It seems that cryptswap is working correctly on 17.10 with the kernel 4.13.0-36-generic on a different machine using the same test as described above. I tried the same kernel (4.13.0-36) on 18.04 (machine used in original post) and it still fails. Of course, I checked that the swap appears in /proc/meminfo. Hope this provides a clue.
[FYI, I'm using 4.13.0-36 rather than 4.13.0-38 because of a bad firmware interaction with 4.13.0-37 and 4.13.0-38 that results in CPU lockups]