With the working from home due to COVID-19, I decided it was finally time to upgrade my service. I moved up to the gigabit plan (mostly for the extra upload bandwidth), and that also required a new modem, so bought an Arris SB8200. It's DOCSIS 3.1, but is apparently synch'ing with my CMTS via DOCSIS 3.0, so these tests are with it in that mode.
I ran a couple raw wired performance tests, and saw the expected ~940Mbps download, but upload was seesawing all over the place. Per http://fast.com, download latency was negligible, but the upload was up well over 200ms.
So I moved behind my home router (WRT1900AC running OpenWRT), and ran a set of tests with https://flent.org.