Comment 1 for bug 1826662

I have exactly the same problem, but I want to add that I got this in 18.04 as well...

Both systems are fresh installation with only 'apt update && apt upgrade' done.

On both systems is same version of snap

snap 2.38+19.04
snapd 2.38+19.04
series 16
ubuntu 19.04
kernel 5.0.0-13-generic

snap 2.38+18.04
snapd 2.38+18.04
series 16
ubuntu 18.04
kernel 4.15.0-47-generic

I found out that this service is freezed:
snapd.seeded.service - Wait until snapd is fully seeded
   Loaded: loaded (/lib/systemd/system/snapd.seeded.service; enabled; vendor preset: enabled)
   Active: activating (start) since Sun 2019-05-12 10:07:11 CEST; 56min 10s ago
 Main PID: 48141 (snap)
    Tasks: 9 (limit: 4617)
   CGroup: /system.slice/snapd.seeded.service
           └─48141 /usr/bin/snap wait system seed.loaded

May 12 10:07:11 xxxxxxxxxxx systemd[1]: Starting Wait until snapd is fully seeded...

Error when trying to install tools is same:
"too early for operation, device not yet seeded or device model not acknowledged"

Can't install any snap tools on 2 completely new systems.

Tried installing snapd on one of my servers with 18.04
snap 2.38+18.04
snapd 2.38+18.04
series 16
ubuntu 18.04
kernel 4.4.38-std-1

It seeded in few seconds correctly:
● snapd.seeded.service - Wait until snapd is fully seeded
   Loaded: loaded (/lib/systemd/system/snapd.seeded.service; enabled; vendor preset: enabled)
   Active: active (exited) since Wed 2019-05-15 19:43:42 UTC; 2min 6s ago
  Process: 31246 ExecStart=/usr/bin/snap wait system seed.loaded (code=exited, status=0/SUCCESS)
 Main PID: 31246 (code=exited, status=0/SUCCESS)
    Tasks: 0 (limit: 2393)
   CGroup: /system.slice/snapd.seeded.service

May 15 19:43:40 xxxxxxxxx systemd[1]: Starting Wait until snapd is fully seeded...
May 15 19:43:42 xxxxxxxxx systemd[1]: Started Wait until snapd is fully seeded.

What might help that where it is working is server that runs for some time, it is VPS virtualized with KVM
Where it doesn't work are Hyper-V virtualized boxes...