Disabling Cloudflare Web Analytics
If your Cloudflare-hosted website has Web Analytics disabled at the domain level but loads the beacon script (static.cloudflareinsights.com/beacon.min.js) anyway, here's the steps I followed to fix it for my own website.
From the Account Home screen’s “Domains” tab, click the custom domain you want to configure (in this example, I clicked the link for gasco.st in the table of domains):

Then from the domain’s dashboard, enable Real User Measurements (RUM):
- Analytics & logs > Web analytics
- Click “Enable Globally”

Back in the user dashboard, open the Web Analytics settings:
- Click where it says “[email protected]’s account” (or whatever the associated user email is)
- Analytics & logs > Web analytics
- In the box for the affected domain, click “Manage site”

Now disable Real User Measurements (RUM):
- Choose “Disable”
- Click “Update”

That fixed it for me! Judging from a few other posts I saw on the Cloudflare Community board, it looks like I'm not the only one, so I hope this helps some other folks. Cloudflare might update their dashboard in the future, so the specific steps and UI might change.