I am running server with Permafrost modpack. There are about 12 structures added and they seem to generate in world.
However, console output is spammed with messages:
[Server thread/WARN] [co.nh.sh.ShulkersSuperSimpleStructureSystem/]: Structure map is empty. This should only happen if user hasn't added any structures

Those occur in groups - over 50 in same second every now and then (not constantly).
Other console messages that are show interleaved are:
[Server thread/INFO] [betterdefaultbiomes/]: Swamp trees added to: TRAVERSE:LUSH_SWAMP

Weird, I'll have to take a look when I get some time. That message was only supposed to show up when you load the world, but I hacked things back together quickly in, I think, 16.2 after mojang made some major changes to structures. Whatever version they added datapack biomes iirc.

I can limit the message to only print once pretty easily if I get my dev environment set up again, although I'm curious why it's getting called so many times. I'm guessing it isn't causing lag spikes though if it's only printing 50ish lines, so I just need to stop it from polluting the logs.

Because of those better biome messages, and where I have that debug message, I think one of the mod in the pack may be causing all the setup events to run again periodically. Idk why it would do that, but there must be a good reason since that has to generate some lag in such a large modpack