Specifying the renderer without apiVersion: 2 (e.g. renderer: <fn>) causes falling back to the legacy string-based rendering even with semantic rendering APIs, i.e. no DOM-patching can be performed.
And according to UI5/openui5#2822, there won't be any implicit setting of the flag either.
Topics that mention renderer: <fn> should be all updated; informing that renderer: <fn> should no longer be used and that apiVersion: 2 should be explicitly set. E.g.:
renderer: function(oRM, oControl) {/*...*/}
renderer: {
apiVersion: 2,
render: function(oRM, oControl) {
// ...
}
}