I tend to take covers off, check for any water or dirt and clean up, check the wiring looms and connectors for any damage or corrosion, then clean up where required, put some corrosion defence on if you can, works as a barrier layer.
Check other bits as well, battery and terminals, again clean and put barrier spray on it.
Always worth taking the chain off and feeling the pedals turning for any notchiness or issues, bearings can be worn or damaged, if this occurs then there’s a fair few motor refurbishers and repair shops around.
Shouldn’t be too much hassle overall, i’d avoid any predictive maintenance style mods, like putting waterproof compounding over the connectors unless ingress is an actual issue, again the motor is a pretty basic piece of machinery, same with the controller and so on, most issues i’ve found is down to bad design and bad QC, so show up pretty quickly during ownership!