Well, you can type them by hand

Weave is at least encrypted, dunno about link since I rarely use Opera.

MicroB supports XBEL so if you Save As your bookmarks from Konqueror for instance, you can directly use them in MicroB.

On the other hand Fennec supports the standard HMTL for Mozilla.

Konqueror exports both HTML and Opera's adr files. Opera can export .adr too.

The problem is to find where to place them but it should work.