Same here, I love the UDM Pro SE. Blocking application layer stuff like QUIC is just a couple clicks away. It has decent intrusion detection and response alongside other easy to configure firewall settings.
I'm reallt happy with it.
Are you doing persistence (keep settings/data after reboot) with Unifi OS 3?
What do you mean by "QUIC vulnerabilities are a 3 or 4 packet compromise"?
QUIC connections do not set an upper bound on the amount of data buffered when reading post-handshake messages, allowing a malicious QUIC connection to cause unbounded memory growth.
I like Google Dart and other Google products but I see too many potential issues with QUIC. From my personal experience it has behaved suspiciously on my network.