My domain is:
https://www.tragoa.com
I received the email about updating to ACMEv2.
I believe I updated what I needed to.
How do I test that I am now running ACMEv2? Or how can I test that ACMEv2 is being used when my certificate is renewed?
Thank you and sorry if this should be obvious 
It depends mainly on the client used.
For certbot, or certbot-auto, you can simply add --dry-run to the command (usually run in cron or systemd) and it should show you the appropriate (pass/fail) response.
[you can also look through the LE log files to ensure acme-v02 is being used]
So, what do we need to look for?
Can I tell from requests to https://acme-staging-v02.api.letsencrypt.org/acme/acct (in /var/log/letsencrypt/letsencrypt.log) that aCMEv2 is used?
It seems so. The above is from certbot v1.0.0; certbot 0.9.3 (on another machine) talks to https://acme-v01.api.letsencrypt.org/
Anything with v02 implies that is should be using acmev2 client.
Anything with v01 implies that is should be using acmev1 client.
So, if you are still seeing v01, you may need to update that client.