Ventura 13.1 'Protect Mail Activity' not working in Apple Mail

Since updating to 13.1 the other day, with 'Protect Mail Activity' enabled, all messages are being delivered without the remote content. A banner above each message says "Your network preferences prevent content from loading privately." and shows me a button to "Load Content Directly", but according to the Apple Help documentation, that's not what is supposed to happen. (And, prior to installing the 13.1 update, that was not happening).

After researching this, I attempted to disable Private Relay in iCloud settings, but it is extremely slow to load that UI, and when it does load, if I click the "Turn Off" button, I see a notification popup that says, "Private Relay Unavailable. Your system settings are incompatible with Private Relay."

So, a) Private Relay on my account appears to be in an "on" state; and, b) I have no way of knowing which specific "system settings" are incompatible.

I found this article, but since I have an active iCloud+ subscription, I should, technically, be able to use the Private Relay feature. (and the "pf.conf" file on my computer is bone stock.)

• MacBook Air M2
• I have an active iCloud+ subscription.
• I have rebooted - it doesn't change anything.
• Advanced Data Protection is not enabled.
• My VPN is not enabled.

Is this a known bug with 13.1? Mail started to behave this way only after updating to 13.1 the other day. I didn't change any of the settings I had been using previously.

I'm not even sure that the problem loading content in Apple Mail is related to Private Relay, but there is no way for me to test the hypothesis since Private Relay is not functioning on my computer.

If I don't want to have to click the "Load Content Directly" button on each and every email message, my only option is to completely disable "Protect Mail Activity" (Apple Mail > Settings > Privacy). And sure, I can do that, but then I'm not getting the benefit of this privacy feature - it should work.