That is normal behavior and nothing new; this also happened in the days before 2.80. By pressing I twice, you set a Keyframe. If there are no Keyframes, Blender doesn’t know what to use as Available….
Curiously enough, even without any Keyframes, you can select Available as the Keying Set in the Timeline (probably a bug/oversight):

but Blender will throw an Error (“No suitable context info for active keying set”), when you then actually try to use that by hitting I.