Prerequisites for restore to vanilla firmware?

[Coffeesurfers]

Running a RT-AX88U on latest merlin firmware and wanted to rollback to the vanilla Asus firmware.
Is there any need to do a factory reset afterwords or just flash the default firmware and be done with it?

 

[ColinTaylor]

A factory reset afterwards is recommended. Merlin makes some underlying configuration changes that are not backwardly compatible with the stock firmware.

Reverting · RMerl/asuswrt-merlin.ng Wiki · GitHub

 

[Tech9]

Is there any need to do a factory reset afterwords

There is a lazy way - disable all Asuswrt-Merlin specific features, flash Asuswrt on top and reset only if issues arise. You have to know well the differences between Asuswrt and Asuswrt-Merlin firmware. If it doesn't work - flash Asuswrt on top, reset + initialize (or WPS reset), configure manually.