The problem is still ongoing on 20.04. I have to open the console daily and run the following commands, due to snapd starts to use my SSD non-stop when I restart. This is faking as `updating Chromium`.

sudo kill -9 $ (pgrep -fn snapd)
sudo systemctl stop snapd
sudo systemctl stop snapd.socket
sudo systemctl stop snapd.service


snap changes
                         
ID   Status  Spawn                     Ready  Summary
76   Doing   2 days ago, at 14:56 MSK  -      Автоматически обновить "chromium" пакет


sudo pidstat -d -T ALL -p `pidof snapd` 5

18:58:15      UID       PID   kB_rd/s   kB_wr/s kB_ccwr/s iodelay  Command
18:58:20        0      1108      0,00   4024,00      0,00       0  snapd


sudo fnotifystat

Total   Open  Close   Read  Write     PID  Process         Pathname
 57.0   18.0   18.0   21.0    0.0     1108 snapd           /var/lib/snapd/assertions/asserts-v0/model/16/generic/generic-classic
 55.0   18.0   18.0   19.0    0.0     1108 snapd           /var/lib/snapd/assertions/asserts-v0/serial/generic/generic-classic/bd2c60ac-7492-417f-ad47-f1fbcf7e8656
 54.0   18.0   18.0   18.0    0.0     1108 snapd           /var/lib/snapd/assertions/asserts-v0/model/16/generic/generic-classic/active
 54.0   18.0   18.0   18.0    0.0     1108 snapd           /var/lib/snapd/assertions/asserts-v0/serial/generic/generic-classic/bd2c60ac-7492-417f-ad47-f1fbcf7e8656/active
 36.0   18.0   18.0    0.0    0.0     1108 snapd           /var/lib/snapd
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.4l5jJQdW0sP3~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.4nyNYbyTTJ21~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.54s0KBgLsdSg~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.5ydLLQG7tC30~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.8k0RWXmCjWC8~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.BHfwQMjR6PSV~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.CVcTY7Bmfmdm~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.DpPCvll2h5tG~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.GKBdLMJLJt5t~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.R6jlBXQmTWG7~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.chY4phGDgT2v~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.djJ2sckH3xK0~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.gsxWS3XBnxS8~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.hqsxj4M83rLD~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.mlfyStjYcShW~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.mpfTr1J1pjjG~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.rCTJHYgY9gYh~
  4.0    1.0    1.0    0.0    2.0     1108 snapd           /var/lib/snapd/state.json.rDkhknkNqB3F~


Reading from the `/var/lib/snapd/assertions/...` files, it's just a "device-key".
Writing to `/var/lib/snapd/state.json` and 2 files with subnames like `state.json.gTFjQFf8Kpps` it is fake. It writing each second and change only the timestamp string in the files.
No any traffic recieving from net.