i made my way to the stronghold and opened up the end.
i now bridged around 5000 blocks out and still did not found any end city / floating boat.

are there no elytrys in this modpack ?

There are End cities, however due to BYG, end highlands are a bit more rare, and from what i've found that's where the cities spawn.

I don't know if it's a problem, but of the 8 endcities I found, only 2 had the boat with the elytra.

There are downed end ships to be found, with chests, and some of them contain a map to an end city. HTH.

Just spawned a new world just to make sure and they are indeed still there but rarer due to the comment above about new features being added to end end.