Screenshot - why can't I download this transcript? You can't SaveAs, and you can't Copy&Paste.

Hi Mike,
I haven't tested this specifically for Phone Call transcripts, but based on how Omnichannel transcripts are stored in Dataverse, it may be worth checking whether the transcript content is stored as an Annotation (Note) linked to an msdyn_transcript record.
Microsoft documents the msdyn_transcript table as the entity that stores communication transcripts, and the Dataverse Annotation table contains attachment content in the documentbody column.
What I would try is:
msdyn_transcript record for the Phone Call.documentbody field, which may contain the transcript attachment.For example:
GET https://<org>.crm.dynamics.com/api/data/v9.2/annotations
?$select=annotationid,filename,documentbody,mimetype,filesize,createdon,notetext
&$filter=_objectid_value eq '<transcript-id> and objecttypecode eq 'msdyn_transcript''
if the transcript record exists in the msdyn_transcript table.
That said, I haven't verified whether the newer Phone Call "Call Summary" experience uses exactly the same storage model. If you test it and find a transcript-related Annotation record, I'd be interested to hear whether the documentbody contains the full transcript text.
Hope this points you in the right direction.