Needs a corresponding change in openshift/router too.
Verified with 4.5.0-0.nightly-2020-05-30-025738 and the issue has been fixed.
After annotating the ingresscontroller with ingress.operator.openshift.io/unsupported-disable-http2="true", the Env ROUTER_DISABLE_HTTP2=true is added to Deployment and the reencrypt route with custom cert uses HTTP1.1 now.
$ oc -n openshift-ingress-operator annotate ingresscontroller/default ingress.operator.openshift.io/unsupported-disable-http2="true"
$ oc -n openshift-ingress rsh router-default-758df89759-6v9qn
sh-4.2$ env | grep HTTP2
$ curl --resolve test-reen.example.com:443:a.b.c.d https://test-reen.example.com -k -I
HTTP/1.1 200 OK
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.