I tested this on 20.04 LTS server where I had no snapd installed initially, and can confirm the issue in this (different, due to 20.04 LTS) setup.
I installed snapd using apt. I could then immediately complete "snap inst<tab>" to "snap install", but I cannot complete "snap install certb<tab>" to "snap install certbot". Nothing visually changes when pressing tab there.
I tested this on 20.04 LTS server where I had no snapd installed initially, and can confirm the issue in this (different, due to 20.04 LTS) setup.
I installed snapd using apt. I could then immediately complete "snap inst<tab>" to "snap install", but I cannot complete "snap install certb<tab>" to "snap install certbot". Nothing visually changes when pressing tab there.