You can start tracking the 3.19/stable instead of stable.
By doing so, your LXD installation will not autoupgrade to LXD 3.20, when it is made available next week.
$ sudo snap switch lxd --channel=3.19/stable
$ sudo snap refresh
When you feel comfortable to upgrade to 3.20 (after you have tested 3.20), you can switch to 3.20/stable.