Minecraft 1.16.5 on a existing Server with Forge 36.2.22
lostcities-1.16-4.0.11-beta.jar

After experimenting for a while, we used your mod for the first time on our server and created a Lost Cities dimension.
We used the Line "dimensionsWithProfiles = ["lostcities:lostcity=onlycities"] in the common.toml file in the Config Folder on our Server.
Like we wanted, nothing changed to our Overworld and the city was created just fine in its own dimension (111).
After taking a few screenshots and playing with the daytime i realized that the sun simply stopped. No movement even after more than an hour realtime. When using the /time query command, i can confirm that time flows normal, the tickrate is normal, mobs spawn and flowers grow. The Sun just stopped, Skylight stays at 15. We use no Mods to adjust the Day/Night Cycle or sleeping. It even worked for a few minutes at the beginning. The command /gamerule doDaylightCycle true helps nothing. All other dimensions work without problems.
No redstone or command blocks where used. Even deleting the configs and lostcities map folders helped nothing. The sun stays in the exact same spot in the new created dimension without movement.