Music for alto recorder is usually written in treble clef, with concert pitch and notated pitch the same. That puts the instrument’s lowest note on the f in the lowest space on the clef, and its highest note (usually) on the g on the 4th ledger line above the clef.
However, sometimes alto recorder music is written an octave lower than it sounds, with the lowest note being on the 3rd ledger line below the staff and the highest note (usually) on the g on the top line of the staff. When music is written this way, it seems reasonable to me to write it as treble clef+8va and treat it analogously to soprano recorder.
In addition, there is a sopranino recorder that is an octave above an alto recorder. This instrument does not seem to appear in Dorico’s library at all. I would think that the right way to treat it would be analogously to the soprano: if transposed, have it sound an octave higher than written; if not transposed, use treble clef+8va and have it sound as written.
I have never seen music written for sopranino that is transposed an additional octave, unlike music written for alto.