As per Kroki server readme, under Manual install, install the following dependencies:

$ sudo pkg install openjdk8 graphviz erd svgbob

As per Install Kroki:

Manual installation

You can also make a customized manual installation that suits your needs.

To do this, you will need to manually install the Kroki gateway server as a standalone executable jar, install each diagram library that you want to use, then run the gateway server jar file.

You are responsible for managing diagram library installations on your system.

Find how to make a manual installation on the Manual installation page.

$ mkdir -p ~/scratch/kroki-server
$ cd ~/scratch/kroki-server

$ pwd
/usr/home/dusko/scratch/kroki-server

You can download the latest standalone executable jar from the GitHub releases page.

At the time of writing, the latest version of Kroki is 0.16.0.
(Retrieved on Feb 25, 2022)

$ fetch \
 https://github.com/yuzutech/kroki/releases/download/v0.16.0/kroki-server-v0.16.0.jar

$ file kroki-server-v0.16.0.jar
kroki-server-v0.16.0.jar: Java archive data (JAR)

Start a web server:

$ java -jar kroki-server-v0.16.0.jar

The above command starts the web server on port 8000. You can change the port using an environment variable, or a Java system property named KROKI_PORT.

With a Web browser, open http://localhost:8000/.

References:
https://kroki.io/
https://demo.kroki.io/
https://kroki.io/examples.html
https://docs.kroki.io/kroki/
https://docs.kroki.io/kroki/setup/install/
https://docs.kroki.io/kroki/setup/manual-install/
https://docs.kroki.io/kroki/setup/configuration/
https://github.com/yuzutech/kroki
https://github.com/yuzutech/kroki/tree/main/server
https://docs.kroki.io/kroki/setup/http-clients/
https://docs.kroki.io/kroki/setup/kroki-cli/
https://github.com/yuzutech/kroki/tree/main/server
https://github.com/yuzutech/kroki/releases

https://github.com/httpie