Issues I've found directly: 1. Seaside still uses #subStrings: instead of substrings: on several places. #subStrings: is deprecated since April 2015.
2. The Seaside control panel icon in menu is not displayed => the icon expression in WAPharoServerAdapterSpecBrowser(class)>>menuCommandOn: returns a blank icon because it is not found Changing to: menuCommandOn: aBuilder <worldMenu> (aBuilder item: #ServerAdapterBrowser) order: 0.21; parent: #Tools; label: 'Seaside Control Panel'; icon: (Smalltalk ui icons seasideAdaptorRunningIcon); action: [ WAPharoServerAdapterSpecBrowser open ] will fix that. 3. Running/stopped icons in Server adopter are not shown in Pharo 5. Change to iconForAdaptor: anAdaptor ^ anAdaptor isRunning ifTrue:[Smalltalk ui icons seasideAdaptorRunningIcon] ifFalse:[Smalltalk ui icons seasideAdaptorStoppedIcon ] to make it work.