Day 2 update:
The documents say to have this config file at ./config/plugins.ts, which is not working for me.
Following this thread I have placed the file at ./config/env/production/plugins.js
Now I can build locally, but on the server I get this error:
[2023-05-05 17:03:50] $ strapi start
[2023-05-05 17:03:56] Error: Could not load js config file /home/app/config/env/production/plugins.js: originalConfigFn is not a function
[2023-05-05 17:03:56] at loadJsFile (/home/app/node_modules/@strapi/strapi/lib/core/app-configuration/load-config-file.js:18:11)
[2023-05-05 17:03:56] at loadFile (/home/app/node_modules/@strapi/strapi/lib/core/app-configuration/load-config-file.js:35:14)
[2023-05-05 17:03:56] at /home/app/node_modules/@strapi/strapi/lib/core/app-configuration/config-loader.js:18:18
[2023-05-05 17:03:56] at Array.reduce (<anonymous>)
[2023-05-05 17:03:56] at module.exports (/home/app/node_modules/@strapi/strapi/lib/core/app-configuration/config-loader.js:15:6)
[2023-05-05 17:03:56] at module.exports (/home/app/node_modules/@strapi/strapi/lib/core/app-configuration/index.js:58:21)
[2023-05-05 17:03:56] at new Strapi (/home/app/node_modules/@strapi/strapi/lib/Strapi.js:82:23)
[2023-05-05 17:03:56] at module.exports (/home/app/node_modules/@strapi/strapi/lib/Strapi.js:573:18)
[2023-05-05 17:03:56] at module.exports (/home/app/node_modules/@strapi/strapi/lib/commands/actions/start/action.js:24:10)
[2023-05-05 17:03:56] at processTicksAndRejections (node:internal/process/task_queues:96:5)
[2023-05-05 17:03:56] error Command failed with exit code 1.
[2023-05-05 17:03:56] info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.