Comment 5 for bug 2031409

You can run:
juju --debug --logging-config "#charmhub=TRACE" info --base ubuntu@22.04 ubuntu

To get the concrete request and responses. from Charmhub.

I see that Charmhub is returning a response for:
        {
            Channel: transport.Channel{
                Name: "candidate",
                Base: transport.Base{Architecture:"amd64", Name:"ubuntu", Channel:"16.04"},
                ReleasedAt: "2022-09-15T15:21:00.599964+00:00",
                Risk: "candidate",
                Track: "latest",
            },
            Revision: transport.InfoRevision{
                ConfigYAML: "",
                CreatedAt: "2022-09-15T14:31:52.411705+00:00",
                Download: transport.Download{HashSHA256:"", HashSHA384:"", Size:2113928, URL:""},
                MetadataYAML: "",
                BundleYAML: "",
                Bases: {
                    {Architecture:"amd64", Name:"ubuntu", Channel:"16.04"},
                    {Architecture:"amd64", Name:"ubuntu", Channel:"18.04"},
                    {Architecture:"amd64", Name:"ubuntu", Channel:"20.04"},
                    {Architecture:"amd64", Name:"ubuntu", Channel:"22.04"},
                },
                Revision: 21,
                Version: "21",
            },
        },

and
        {
            Channel: transport.Channel{
                Name: "stable",
                Base: transport.Base{Architecture:"arm64", Name:"ubuntu", Channel:"22.04"},
                ReleasedAt: "2023-05-26T00:01:57.835985+00:00",
                Risk: "stable",
                Track: "latest",
            },
            Revision: transport.InfoRevision{
                ConfigYAML: "",
                CreatedAt: "2023-05-19T14:05:37.530491+00:00",
                Download: transport.Download{HashSHA256:"", HashSHA384:"", Size:2139977, URL:""},
                MetadataYAML: "",
                BundleYAML: "",
                Bases: {
                    {Architecture:"amd64", Name:"ubuntu", Channel:"18.04"},
                    {Architecture:"arm", Name:"ubuntu", Channel:"18.04"},
                    {Architecture:"arm64", Name:"ubuntu", Channel:"18.04"},
                    {Architecture:"i386", Name:"ubuntu", Channel:"18.04"},
                    {Architecture:"ppc64", Name:"ubuntu", Channel:"18.04"},
                    {Architecture:"amd64", Name:"ubuntu", Channel:"20.04"},
                    {Architecture:"arm", Name:"ubuntu", Channel:"20.04"},
                    {Architecture:"arm64", Name:"ubuntu", Channel:"20.04"},
                    {Architecture:"i386", Name:"ubuntu", Channel:"20.04"},
                    {Architecture:"ppc64", Name:"ubuntu", Channel:"20.04"},
                    {Architecture:"amd64", Name:"ubuntu", Channel:"22.04"},
                    {Architecture:"arm", Name:"ubuntu", Channel:"22.04"},
                    {Architecture:"arm64", Name:"ubuntu", Channel:"22.04"},
                    {Architecture:"i386", Name:"ubuntu", Channel:"22.04"},
                    {Architecture:"ppc64", Name:"ubuntu", Channel:"22.04"},
                },
                Revision: 24,
                Version: "24",
            },
        },

I'm guessing that Juju is getting confused because it is seeing the old rev 21 in an 'all' channel, and then using that to determine that it also supports 22.04, but then sees rev 24 in the 'amd64' channel.

Note that charmhub is returning ~3000 lines of response for "what versions of Ubuntu are available", which means that it is confusing for all parties involved.