PROBABLY WON'T FIX:
Embedded rules language not updated when language is set (in Analyse, Game and Problems)
If new live game starts in background, "new game" notify OK but not first move.

"FreeBoard", re-using a lot of Board logic, but with SVG (empty) board + SVG (empty) reserves.
Will be used for variants with custom non-rectangular board (Hex, at least)
Or, with other board shapes (see greenchess.net for example)

Merge variants 1, 2 (3) into one with sub-variant selection when starting a game (New Game + vs engine + analyse)
E.g. Checkered 1 & 2 into one, and so on.
Need additional field in variant code... in a generic way (radiobutton or select or checkbox?)

#New variants:
Chessplode
Tablut

https://brainking.com/fr/GameRules?tp=128 Massacre Chess

CWDA : need game options (also useful at least for Monster)
PizzaKings https://www.chessvariants.com/unequal.dir/pizza-kings.html
https://en.m.wikipedia.org/wiki/Chess_with_different_armies#Pizza_Kings%5B11%5D_(John_Lawson)

https://www.chessvariants.com/other.dir/nemoroth.html :-)