I tried but it returns errors
Sorry, can't help you much. Last time I checked Asuswrt-Merlin firmware still had issues with wireless node discovery. Unfortunately, AiMesh is closed source and what causes the issue is unknown. Attempts to fix it were made even on Asus side. You have better chances with the same code base routers (all on 388), worse chances with mix and match on different code base (388 with 386). It may work between specific models and fail with others. If your specific combination fails - you have to find own workaround.
I can only give you a hint what I have tried and it worked:
- Run stock Asuswrt on the nodes, Asuswrt-Merlin is not needed there, wireless nodes are Repeaters.
- Run closest release stock Asuswrt to current Asuswrt-Merlin on the main router, do
minimal setup just to get to AiMesh configuration.
- Add the nodes wirelessly with all routers running stock Asuswrt, reboot few times to make sure they reconnect properly.
- Upgrade the main router to Asuswrt-Merlin
without reset and do the rest of your configuration manually. Don't worry, it works.
Additionally:
- If the above seems too complicated just run the extra routers as Repeaters on stock Asuswrt. The result is about the same without Guest Network to nodes.
- In a long run get a proper/better "mesh" system or if you want to stick with AiMesh upgrade your routers to the same model running the same firmware.
- Do "how much is my time worth" calculation and decide which way you want to go for further network upgrades. Troubleshooting time will help you decide.
- Reusing old equipment is not always the best idea for network expansion. At some point it's better to start fresh and explore other possible options.
Good luck!