I just check the Market and did not see anything that was compatible with Version 4.0. There were some changes from version 3.3 to 4.0 they may have broken that content pack.
I’m not sure Docker works like that, but creating your own Content pack for Nginx is possible.
Can you link to the content pack you’re referring to please? If it’s a community content pack (e.g., not maintained by Graylog) then you’ll need to reach out to the maintainer to see if they plan on supporting 4.0.
The only concern I am having right now is those highlighted values showing static fields. I am going to tell my IT team to send logs now. Will see if it is working as expected.