The ages of Myst V, Crowthistle, Hex Isle and MagiQuest are not automatically installed on the Shard - you have to buy these games in order to play them online. After doing so, you can use Drizzle exactly the same way as offline to convert the ages. Just choose your DI Client as "POTS folder". However, please note that the ages need to be converted with a specific version of Drizzle or the server might reject them:
Myst V: Drizzle 30
Crowthistle: Drizzle 29 or 30
HexIsle: Drizzle 30
MagiQuest: Drizzle 29 or 30
Please note that the GoG version of Myst V has been reported *not* to work on Deep Island! There have been some modifications made to the game (presumably to support more languages), which make it incompatible with the "original" Myst V as published by Ubisoft. The same holds for the "Gold" version of Myst V. The "White" version seems to work fine. See this discussion for more details.