Comment 15 for bug 1827286

I played a bit with my config and found:
- the error is even reported if /home is set to mount something that won't work (e.g. non existent server), so it must failing early in the autofs processing
- one can mount things manually (as expected)

The difference is only 5.1.1-1ubuntu3 to 5.1.2-1ubuntu3 as upstream doesn't make a lot of changes anymore. Unfortunately I found no obvious change in between those versions which would be responsible for that.

The fail I get for the direct mount to /home.
With your symlink trick (that you mentioned was for a different case in the past) I can mount it thou:

ubuntu@xenial-autofs-client:/$ cat /etc/auto.master | grep -v '^#'
+dir:/etc/auto.master.d
+auto.master
/vol /etc/auto.nfs --timeout=0,nosymlink,-fstype=nfs,nfsvers=3,rw,hard,intr,rsize=8192,wsize=8192
ubuntu@xenial-autofs-client:/$ cat /etc/auto.nfs | grep -v '^#'
home 192.168.122.54:/mnt/sharedfolder
ubuntu@xenial-autofs-client:/$ ll /home
lrwxrwxrwx 1 root root 9 May 6 08:40 /home -> /vol/home/

=> works

I can confirm on Xenial that I can mount it fine with the symlink in place.
Circling back to your report now a reboot should break it, but even throughout a reboot that works fine.

I don't know why the same doesn't work for you - it does for me.
But we can instead continue to use the direct mount case as that recreates your issue.