Yes, Amiga Workbench up to version 1.3 ships with a speech synthesizer (it was removed from later versions due to licensing issues, but will still work fine if manually installed.)
This is a really interesting subject; I'm curious to hear more about accessibility on vintage computers.
Computers: Amiga 1200, DEC VAXStation 4000/60, DEC MicroPDP-11/73
Synthesizers: Roland JX-10/SH-09/HS-80/MT-32/D-50, Yamaha DX7-II/V50/TX7/TG33/FB-01, Korg MS-20 Mini/ARP Odyssey/DW-8000/M1, Ensoniq SQ-80, E-mu Emax HD/Proteus-2, Casio CZ-5000, Moog Satellite, Sequential Circuits Prophet-600
"'Legacy code' often differs from its suggested alternative by actually working and scaling." - Bjarne Stroustrup