Lunar Client has a tendency to break on LEM a lot
. It has reached a point where the game is unplayable, and here we have a list of everything it breaks.
Current known issues
1 - In the host menu, the chat and most Vanilla UI elements is not visible, and it is only possible to start the game with /trigger 4j.gamecfg at this point.
2 - Commonly, all entities (Players, Chests, Armor Stands, etc.) fail to render, making them invisible. This makes the game essentially unplayable at this state.
3 - Many UI elements that use the bossbar to render break, such as the battle banner and panorama.
What you can do
While you can't play with Lunar Client, you can use alternatives:
1 - Legacy Console Experience
: Legacy Console Experience is a modpack that emulates the look of LCE, and has perfect LEM compatibility without compromises.
2 - Console-idated
: Console-idated is another modpack that attempts to mimic the look of LCE, and has LEM compatibility with few compromises.
3 - Fabulously Optimized
: FO is a modpack designed to improve the performance of Minecraft significantly and works pretty well with LEM, but adds a shadow to the hotbar UI.
4 - OptiFine
: OF is a mod designed to optimize the game, but is not the most preferable to use on LEM and can cause issues to other mods as well.
5 - Vanilla Minecraft
: Vanilla Minecraft works fine on LEM with no LEM-specific issues, but Vanilla is very poorly optimized. I recommend anything listed above over Vanilla.