Hello Julian,
Thank you for the response. I have checked and these are the errors that I have received.
nodebb@localhost:~/nodebb$ ./nodebb dev
NodeBB v3.5.0 Copyright (C) 2013-2023 NodeBB Inc.
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it under certain conditions.
For the full license, please visit: http://www.gnu.org/copyleft/gpl.html
Clustering enabled: Spinning up 2 process(es).
2023-11-09T02:02:11.955Z [4568/16724] - verbose: * using configuration stored in: /home/nodebb/nodebb/config.json
2023-11-09T02:02:11.950Z [4567/16723] - verbose: * using configuration stored in: /home/nodebb/nodebb/config.json
2023-11-09T02:02:11.964Z [4567/16723] - info: Initializing NodeBB v3.5.0 http://localhost:4567
2023-11-09T02:02:11.964Z [4567/16723] - verbose: * using mongo store at 127.0.0.1:27017
2023-11-09T02:02:11.965Z [4567/16723] - verbose: * using themes stored in: /home/nodebb/nodebb/node_modules
2023-11-09T02:02:12.054Z [4568/16724] - error: Error: redis-required-for-pubsub
at get (/home/nodebb/nodebb/src/pubsub.js:51:9)
at Object.on (/home/nodebb/nodebb/src/pubsub.js:63:3)
at module.exports (/home/nodebb/nodebb/src/cache/lru.js:105:9)
at module.exports.create (/home/nodebb/nodebb/src/database/cache.js:5:9)
at module.exports (/home/nodebb/nodebb/src/database/mongo/hash.js:6:36)
at Object.<anonymous> (/home/nodebb/nodebb/src/database/mongo.js:187:24)
at Module._compile (node:internal/modules/cjs/loader:1376:14)
at Module._extensions..js (node:internal/modules/cjs/loader:1435:10)
at Module.load (node:internal/modules/cjs/loader:1207:32)
at Module._load (node:internal/modules/cjs/loader:1023:12)
2023-11-09T02:02:12.056Z [4567/16723] - error: Error: redis-required-for-pubsub
at get (/home/nodebb/nodebb/src/pubsub.js:51:9)
at Object.on (/home/nodebb/nodebb/src/pubsub.js:63:3)
at module.exports (/home/nodebb/nodebb/src/cache/lru.js:105:9)
at module.exports.create (/home/nodebb/nodebb/src/database/cache.js:5:9)
at module.exports (/home/nodebb/nodebb/src/database/mongo/hash.js:6:36)
at Object.<anonymous> (/home/nodebb/nodebb/src/database/mongo.js:187:24)
at Module._compile (node:internal/modules/cjs/loader:1376:14)
at Module._extensions..js (node:internal/modules/cjs/loader:1435:10)
at Module.load (node:internal/modules/cjs/loader:1207:32)
at Module._load (node:internal/modules/cjs/loader:1023:12)
[cluster] Child Process (16724) has exited (code: 0, signal: null)
[cluster] Child Process (16723) has exited (code: 0, signal: null)
nodebb@localhost:~/nodebb$
Oh, I think I know why. I totally missed the "Configuring Redis if multiple processes was used". I subconsciously thought that Redis section was related to the Database type to be used like TigerEngine.
My bad