RewriteOptions / UseRewriter behaves inconsistently after upgrading from .net 5 to .net 6

I found a solution that might help someone else who crosses this bridge.

First I created an XML file, IISUrlRewrite.xml and saved it. This part was easy for me since this is almost exactly the same that was in the project back when it was in the .net framework version's web.config:

<rewrite>
<rules>
    <rule name="images redirection">
        <match url="^assets/([0-9]+)/((.*)\.(gif|jpg|jpeg|png|bmp|mp4|mp3|ogg|wav|tiff))$" ignoreCase="true" />
        <action type="Redirect" url="https://****/assets/design/{R:1}/{R:2}" />
    </rule>
    <rule name="capture question redirection">
        <match url="^answers/([0-9]+)/([a-zA-Z0-9]+)/((.*)\.(gif|jpg|jpeg|png|bmp|mp4|mp3|ogg|wav|tiff))$" ignoreCase="true"/>
        <action type="Redirect" url="https://****/answers/design/{R:1}/{R:2}/{R:3}" />
    </rule>
    <rule name="collagebuilder redirection">
        <match url="^assets/collagebuilder/((.*)\.(gif|jpg|jpeg|png|bmp))$" ignoreCase="true" />
        <action type="Redirect" url="https://****/collagebuilder/{R:1}" />
    </rule>
    <rule name="survey theme redirection">
        <match url="^themes/((.*)\.css)$" ignoreCase="true" />
        <action type="Redirect" url="https://****/themes/{R:1}" />
    </rule>
    <rule name="st folder redirection">
        <match url="st/(.*)" ignoreCase="true"/>
        <action type="Rewrite" url="/{R:1}" />
    </rule>
</rules>

Next, modified my Startup / Program (whatever you want) code:

app.UseHttpsRedirection();

        using (StreamReader iisUrlRewriteStreamReader =
        File.OpenText("IISUrlRewrite.xml"))
        {
            var options = new RewriteOptions()
                .AddIISUrlRewrite(iisUrlRewriteStreamReader);
            app.UseRewriter(options);
        }

        //var redirectOptions = new RewriteOptions()
        //    .AddRedirect(@"^/assets/([0-9]+)/((.*)\.(gif|jpg|jpeg|png|bmp|mp4|mp3|ogg|wav|tiff))", $"{surveyConfig.AssetsRedirectUrl}/$1/$2")
        //    .AddRedirect(@"^/answers/([0-9]+)/([a-zA-Z0-9]+)/((.*)\.(gif|jpg|jpeg|png|bmp|mp4|mp3|ogg|wav|tiff))", $"{surveyConfig.AnswerAssetsRedirectUrl}/$1/$2/$3")
        //    .AddRedirect(@"^/assets/collagebuilder/((.*)\.(gif|jpg|jpeg|png|bmp))", $"{surveyConfig.CollageBuilderAssetsRedirectUrl}/$1")
        //    .AddRedirect(@"^/themes/((.*)\.css)", $"{surveyConfig.ThemeAssetsRedirectUrl}/$1")
        //    .AddRewrite("st/(.*)", "/$1", true);


        //app.UseRewriter(redirectOptions);

I'm not sure why the original approach wasn't working for me (reliably), but this seems to do the trick. It's explained in more detail here: https://learn.microsoft.com/en-us/aspnet/core/fundamentals/url-rewriting?view=aspnetcore-6.0