CODA56 Modem(s) suddenly stopped working (long)

I had been using the same setup for two years (personal CODA56 with personal ASUS RT-AX86U behind it). It was working fine up to 2300 Eastern on Sunday 10/11 when I powered down network for night (electricity is expensive in New England).

Monday morning, powered up network, all lights good, got a WAN IP on my router so everything looked normal, but I couldn't access anything on internet.

I was able to ping bare IPs on internet like google DNS (8.8.8.8) so ICMP was being passed and interestingly my PIA VPN client showed green so VPN ports were being at least partially passed (web behavior didn't change whether VPN on or off), but my mail client (which uses TLS/SSL) and every website I tried (which are almost certainly https 443) could not connect.

I turned off my DNS over TLS on my router and switched to standard Google DNS servers to see if my router config was messing with DNS lookups, nothing changed.

Power cycled multiple times to see if updated config or firmware needed to load and then spent two hours on phone with support while we reprovisioned multiple times. Every check from Xfinity side seemed okay, signal looked good. I just couldn't actually use the connection. Level 1 support had reached the limit of what she could do so we scheduled an onsite tech.

Onsite tech verified my connection was good with his portable cable modem. We verified my phones, computer etc. worked normally and could surf via the wifi network from his portable modem. And we ruled out my router as the issue because the same problem persisted when my pc was plugged directly into the CODA56, receiving a public IP from the WAN DHCP and bypassing my router entirely; same issue. For some reason, this modem was not working despite all checks being good.

The possibilities seemed to be bad config stuck in modem, the modem being specifically blacklisted upstream for some reason or a hardware issue. He escalated the ticket to check for any explicit block on the modem's CM MAC but that was going to take a few days. I decided to just go ahead and order another CODA56 modem as well to rule out both blacklisting and a hardware issue. I also performed a factory reset on the old modem in the meantime in hopes that would clear out any bad config and force it to pull a fresh config. No change.

New modem arrived this morning, worked with support to get provisioned when I had issues with app (typo on my part), all checks looked good on link level once I was using correct CM MAC and exact same issue is present in brand new modem.

So it really seems like an updated config or firmware for the CODA56 was pushed out overnight between 10/11 and 10/12 (at least in my region) and is breaking TLS/SSL handshakes from the modems.

So this is my long-winded way of asking: "Help!". Is this a known problem? Any Xfinity support folks who might have an idea where to go next?

Looking back, buying the exact same model of modem was a bit of a self own; I should have gotten an Arris or other supported modem if I thought it was a bad config for the CODA56, but I assumed it either a corrupted config local to my modem or the CM MAC was being specifically blocked and I knew the CODA56 worked well with my network setup.