That's a bug. I've put in a report for it.
You should still have your Opus 9 toolbars, and eveything on them should still work, unless you've done a completely clean install. The toolbars will be turned off but you can turn them back on, copy whatever you want out of them, or even use them instead if you want.
If you did a clean install, here are the buttons.
(See: How to add buttons from this forum to your toolbars)
This is the Opus 9 three-button for Select All / Select None / Invert Selection:
<?xml version="1.0"?>
<button backcol="none" display="both" textcol="none" type="three_button">
<label>Select &All</label>
<icon1>#selectall</icon1>
<button backcol="none" display="both" textcol="none">
<label>Select &All</label>
<tip>Select all the files and folders in the active Lister</tip>
<icon1>#selectall</icon1>
<function type="normal">
<instruction>Select ALL</instruction>
</function>
</button>
<button backcol="none" display="both" textcol="none">
<label>Select &None</label>
<tip>Deselect all files and folders in the active Lister</tip>
<icon1>#selectnone</icon1>
<function type="normal">
<instruction>Select NONE</instruction>
</function>
</button>
<button backcol="none" display="both" textcol="none">
<label>&Invert Selection</label>
<tip>Invert the selection status of all files in the active Lister</tip>
<icon1>#selectinvert</icon1>
<function type="normal">
<instruction>Select INVERT</instruction>
</function>
</button>
</button>
And the one that was next to it, for Select... / Reselect Files:
<?xml version="1.0"?>
<button backcol="none" display="both" separate="yes" textcol="none" type="three_button">
<label>&Select...\tCtrl+S</label>
<icon1>#selectwild</icon1>
<button backcol="none" display="both" textcol="none">
<label>&Select...\tCtrl+S</label>
<tip>Select files and folders in the active Lister by wildcard pattern</tip>
<icon1>#selectwild</icon1>
<function type="normal">
<instruction>Select</instruction>
</function>
</button>
<button backcol="none" display="both" textcol="none">
<label>Reselect Files</label>
<tip>Reselect all files that were used in the previous command</tip>
<icon1>#reselect</icon1>
<function type="normal">
<instruction>Select RESELECT</instruction>
</function>
</button>
</button>
(All those things are in the Edit menu in the default Opus 10 toolbars, too.)