Better to use with my userstle:
Flickr WideScreen - BigONE
https://userstyles.world/style/248/flickr-widescreen-bigone-v-320-usw

This userscript add a Tweak 2025.03 to make Flickr Functional Suite work in Photo page:
I don't know why, but in  photo page clicking on the username (near the Buddy icon), don't open the FFS popup.
But with the GM "View in FlickRiver", it is possible to open it.
So, I add this FlickRiver button in FFS and rename it as "F. Functional S."

Now if you click on it it open the FFS popup.
It Receive too the Color Tags of FFS (When you Hover it, you see them)

I Publish too another version of GM "View in FlickrRiver" to work with this FFS:
In Photo page, It add the FlicRiver button near the new FF button