Some config options which I remember where in 1.12.2 aren't listed in config files in newer version. Are functions like "miltuply loot from trees" unavailable for 1.16.5?

Yes but server configurations are now world-based. This means you need to change the options in saves/[world]/serverconfig/dynamictrees-server.toml instead of in the normal config directory.

By the way, you can also move this file to /defaultconfigs in the root MC directory in order to have them copy over to that location automatically when creating new worlds.

Giant thanks to you!