The original r/TranscribersOfReddit (ToR) was run by an actual non-profit organisation (the Grafeas Group) with a lot of infrastructure built up to support it and keep it running smoothly. When Reddit's API changes happened, we didn't have the resources to move the project somewhere else (and nowhere else was as dreadfully inaccessible as Reddit), so we were essentially forced to shut it down. The communities that exist on Lemmy aren't coordinated, they're just people who used to be part of ToR doing transcriptions in their free time, in a capacity not associated with the Grafeas Group. As such, there isn't really a way to coordinate them.
I just sort by new on the communities I'm subscribed to.
I don't use a screen reader but l do know the answer to this -- alt text on the image is a much better route to go when you have the option, as it means people can find the transcription right next to the image instead of looking for it in the comments. Helping people find our transcriptions in the comments was a challenge on Reddit.