Using only multiple https endpoints with ASP.NET Core (Kestrel) doesn't work - asp.net-core

Question

So we've run into this really weird issue with the URLs on which we want to host our APIs.
We are currently using ASP.NET Core (.NET7) and Kestrel on Windows for self-hosting. We have a certificate and usually everything works as expected.
We typically use the URLs:
"http://abc.ourdomain.com"
"https://abc.ourdomain.com"
this works very well.
If we switch to only use a single:
"https://abc.ourdomain.com"
it works as well.
However, if we switch to only multiple https URLs:
"https://abc.ourdomain.com"
"https://def.ourdomain.com"
none of them works!
Unless we also add a http for either of them:
"http://abc.ourdomain.com"
"https://abc.ourdomain.com"
"https://def.ourdomain.com"
Then they all work!
Which URLs we use are set using:
app.Urls.Add(url)
And we use:
builder.WebHost.ConfigureKestrel(serverOptions =>
{
serverOptions.ConfigureEndpointDefaults(listenOptions =>
{
listenOptions.UseHttps(/*cert info*/);
});
});
to configure Kestrel.
We've tried with https redirection on and off. No difference.
So basically, to sum up it seems like we need at least one http endpoint OR only one single https endpoint. This this makes no sense.
Can someone explain what is going on?

Answer 1

It turns out that this was just the tip of the iceberg of issues we ran into. Coming from .NET Framework 4.8 using OWIN and migrating to .NET7 and ASP.NET Core.
I don't consider this a solution to the problem stated above, we simply never solved it. However when having expectations such as:
those above
being able to host multiple servers on the same port (different URLs)
make it work on older windows servers (Kestrel only worked on 2022 for us)
use registered certs automatically
etc
then Kestrel simply isn't the way to go. Once we switched to HTTP.sys it all worked like a charm. Sure this makes us bound to Windows, but that is the case for us anyway.
There are some good information on how to set it up and what HTTP.sys provides that Kestrel don't here:
https://learn.microsoft.com/en-us/aspnet/core/fundamentals/servers/httpsys?view=aspnetcore-7.0
Please note that I am not suggesting HTTP.sys over Kestrel in general. But it solved our scenario and I hope this info helps others trying to do the same upgrade and are stuck!