GKE Gateway with a wildcard Certificate Manager certificate - google-cloud-platform

Question

I'm trying to set up GKE Gateway with an HTTPS listener using a wildcard certificate managed via Certificate Manager.
The problem I'm facing is not in provisioning of the certificate, which was done successfully following the DNS Authorization tutorial and this answer. I've successfully provisioned a wildcard certificate, which is shown by gcloud certificate-manager certificates describe <cert-name> as ACTIVE and
AUTHORIZED on both the domain and its wildcard subdomain. I've also provisioned the associated Certificate Map and Map Entry (all via Terraform) and created a global static IP address and a wildcard A record for it in Cloud DNS.
However, when I try to use this cert and address in the GKE Gateway resource, the resource gets "stuck" (never reaches SYNC phase), and there's no HTTPS GCLB provisioned as seen via gcloud or Cloud Console.
Here's the config I was trying to use for it:
kind: Gateway
apiVersion: gateway.networking.k8s.io/v1beta1
metadata:
name: external-https
annotations:
networking.gke.io/certmap: gke-gateway
spec:
gatewayClassName: gke-l7-gxlb
listeners:
- name: http
protocol: HTTP
port: 80
allowedRoutes:
kinds:
- kind: HTTPRoute
- name: https
protocol: HTTPS
port: 443
allowedRoutes:
kinds:
- kind: HTTPRoute
addresses:
- type: NamedAddress
value: gke-gateway
I've tried multiple different combinations of this config, including with an explicit IPAddress, or without allowedRoutes. But no matter what I try, it doesn't seem to work. I can only see the initial ADD and UPDATE events in the output of kubectl describe gateway external-http, and there're no logs for it to be found anywhere afaik (since GKE Gateway Controller is part of the GKE Control Plane and without any logging exposed to the customers, from what I understand).
The only time I was able to make either internal or external Gateway to work is when using HTTP protocol, i.e. without certificates. Hence, I think this has to do with HTTPS, and probably more specifically with linking to the managed wildcard certificate.
Additionally, I should mention that my attempts at deploying the Gateway fail most of the time (i.e. the resource gets "stuck" in the same way), even when reusing a previously-working HTTP config. I'm not sure what the source of this flakiness is (apart from maybe some internal quota), but I imagine this is fully expected, as the service is still in Beta.
Has anyone been able to actually provision a Gateway with HTTPS listener and wildcard certs, and how?