Comment 9 for bug 1849665

Hm, at first glance this didn't work with the new kernel and zfsutils-linux package:

root@nsn7:/zfs-test# zfs diff tank/d1@s1 tank/d1
Unable to determine path or stats for object 3 in tank/d1@s1: File exists
root@nsn7:/zfs-test# uname -a
Linux nsn7 5.3.0-21-generic #22-Ubuntu SMP Tue Oct 29 22:55:51 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
root@nsn7:/zfs-test# dpkg -l|grep linux-image
ii linux-image-5.3.0-18-generic 5.3.0-18.19+1 amd64 Signed kernel image generic
ii linux-image-5.3.0-19-generic 5.3.0-19.20 amd64 Signed kernel image generic
ii linux-image-5.3.0-21-generic 5.3.0-21.22 amd64 Signed kernel image generic
ii linux-image-generic 5.3.0.21.24 amd64 Generic Linux kernel image
root@nsn7:/zfs-test#

This was with the existing pool and dataset from the previous test.

Let me try restarting it from scratch:
root@nsn7:/zfs-test# cd
root@nsn7:~# zpool destroy tank
root@nsn7:~# rm -rf /zfs-test/
root@nsn7:~# mkdir /zfs-test
root@nsn7:~# cd /zfs-test
root@nsn7:/zfs-test# truncate -s 10G file.img
root@nsn7:/zfs-test# zpool create -o ashift=12 -O acltype=posixacl -O compression=lz4 -O xattr=sa -O normalization=formD -O dnodesize=auto tank $(pwd)/file.img
root@nsn7:/zfs-test# zfs create tank/d1 -o encryption=on -o keyformat=passphrase
Enter passphrase:
Re-enter passphrase:
root@nsn7:/zfs-test# dd if=/dev/urandom bs=4k of=/tank/d1/somedata.bin count=10240
10240+0 records in
10240+0 records out
41943040 bytes (42 MB, 40 MiB) copied, 0,39306 s, 107 MB/s
root@nsn7:/zfs-test# zfs snapshot tank/d1@s1
root@nsn7:/zfs-test# dd if=/dev/urandom bs=4k of=/tank/d1/somedata2.bin count=10240
10240+0 records in
10240+0 records out
41943040 bytes (42 MB, 40 MiB) copied, 0,265228 s, 158 MB/s
root@nsn7:/zfs-test# zfs diff tank/d1@s1 tank/d1
Unable to determine path or stats for object 3 in tank/d1@s1: File exists
root@nsn7:/zfs-test# uname -a
Linux nsn7 5.3.0-21-generic #22-Ubuntu SMP Tue Oct 29 22:55:51 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

root@nsn7:/zfs-test# apt-cache policy linux-image-5.3.0-21-generic zfsutils-linux
linux-image-5.3.0-21-generic:
  Installed: 5.3.0-21.22
  Candidate: 5.3.0-21.22
  Version table:
 *** 5.3.0-21.22 500
        500 http://br.archive.ubuntu.com/ubuntu eoan-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
zfsutils-linux:
  Installed: 0.8.1-1ubuntu14.1
  Candidate: 0.8.1-1ubuntu14.1
  Version table:
 *** 0.8.1-1ubuntu14.1 500
        500 http://br.archive.ubuntu.com/ubuntu eoan-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     0.8.1-1ubuntu14 500
        500 http://br.archive.ubuntu.com/ubuntu eoan/main amd64 Packages

Same thing.