Tried it on the 3B+ under Ubuntu 18.04 64bit... didn't seem to like it:

@RaspPi:~/zettel$ ./zettelkastend
-bash: ./zettelkastend: No such file or directory

I'm assuming this daemon is 32bit, built under Raspian and it's not happy with the 64bit Ubuntu environment.

Update: It's much happier using Rasbian (Stretch-Lite):

@raspi:~/zettel $ ./zettelkastend getinfo
{
    "version" : 91801,
    "protocolversion" : 70022,
    "walletversion" : 60000,
    "balance" : 0.00000000,
    "blocks" : 295210,
……....

Though the hashrate using 32bit leaves a lot to be desired:

 "hashespersec" : 23597,

But this is really just for a low wattage Full Node, correct?