If you mean what's in the stable repository that changes too often to be viable otherwise if you mean what is on the ISO that is what the blog posts are for.
barrel0luck I've been keeping an eye out if GNOME 3.32 stack has made it to Solus 4 (stable) before trying it out and its difficult to figure out as this doesn't seem to be mentioned anywhere.
It's been in stable since like, May?
https://getsol.us/2019/04/25/gnome-of-thrones/
Solus syncs unstable to stable once a week unless there is an issue with something in unstable / something requires more extensive testing. Then the sync may get postponed for further testing or the changes causing the issues will be reverted and the rest synced to stable.
You can browse packages on stable here (It will show several versions so you need to look carefully for the latest and ignore deltas (They are differences between updates to reduce downloads):
https://packages.getsol.us/shannon
Or searching for package repositories on the dev tracker which won't tell you if its in stable or not but as I said, it syncs once a week so if nothing changes for awhile, its a good indication.
https://dev.getsol.us/diffusion/
Example: https://dev.getsol.us/source/gnome-shell/
Blog posts are also helpful when a new ISO is put out (Hasn't been a new one since Solus 4 iso which didn't contain the update you were after):
https://getsol.us/blog/
