Hi MiroslavI believe the bugs you ran into are more similar to #401296 (G-I interface does not work in UTF-8 mode/input handled in 8859-1) and #394871 ( cdebconf-gtk-udeb: Dead keys do not work with French keyboard (fr-latin9) ) than to #395257.
#395257 ([g-i] keymap change works only once), is about a different bug and recently fixed by fjp, so replying to 401296 and 394871 for relevant parts and dropping 395257.
The Czech keymap does not work as expected. It has two modes: * By default it behaves like an ordinary English/US keymap (this works).By pressing AltGR+number from upper row you should be able to writesome accented letters. That probably works too, but some of the letters are displayed as in different encoding, therefore showing wrong symbols. Please see http://www.debian.cz/~kurem/shots/ d-i.png shows expected output from pressing keys 1-0, g-i.png shows current output from your g-i miniiso.
That's very similar to what Eddy reported: "special" accented letters are displayed with wrong accents or symbols.Talking with Davide on IRC we both agreed that this is related to the way DFB handles input and not to DejaVu glyphs, otherwise also text in translated question description would look weird.
cheers Attilio