Using Monifactory 0.9.10 on server and client, with no additional modifications.

[16Nov2024 12:47:08.402] [Netty Client IO #4/DEBUG] [net.minecraftforge.client.ForgeHooksClient/CLIENTHOOKS]: Received FML ping data from server at 10.0.1.228:24477: FMLNETVER=3, mod list is compatible : false, channel list is compatible: true, extra server mods: {}

[16Nov2024 12:47:08.402] [Netty Client IO #4/INFO] [net.minecraftforge.client.ForgeHooksClient/CLIENTHOOKS]: Client has mods that are missing on server: [zume]

But as stated here,

It should not be used on serverside.

afaik, there are some mods that have a fml flag that let fml know to exclude it from the server modlist compatibility check.

Thanks!

Don't know if this helps, but:
https://docs.minecraftforge.net/en/1.12.x/gettingstarted/structuring/#what-is-mod
(see clientSideOnly, serverSideOnly)

Not sure if it addressed the symptom or not, but I added the clientSideOnly suggestion in this commit. Please test 2.0.0-dev.1 to see if this issue still happens.

Yeah turns out I broke things. Will fix that soon and post another link here when that's done.

Won't start. As it's 4am I'll have to remember to look more later

crash-2024-11-30_04.13.00-fml.txt

Try 2.0.0-dev.2