TileEntity

Delete the config files of these 2 mods (config folder) - if there is no change, use a pre-configured mod pack with these 2 as working base

Does it work with only these 2 mods, without an other mods? If yes, add the rest of your mods one by one or in groups

Check for updates of these 2 mods - maybe there are newer 1.21.1 builds of these

Try other builds of these 2 mods

Maybe some sodium addons (sodium options api etc)

Does it work without Iris?

Remove iceberg, Toggle Enchantments, Legendary Tooltips and Quark

There is another - letsdo-bakery requires doAPI Also add this mod: https://www.curseforge.com/minecraft/mc-mods/do-api If this is still not working, add the new crash-report

The link to the log is wrong

lootintegrations_iceandfire requires lootintegrations Add this mod: https://www.curseforge.com/minecraft/mc-mods/loot-integrations

Make a test without survivalisland

Add the crash-report or latest.log (logs-folder) with sites like https://mclo.gs/ and paste the link to it here

Also remove Biomes We've Gone and add the new crash-report

Does it work without terrablender?

There is nothing mentioned in the logs I suspect Traverse writes invalid data to the world/region files (biome data), which doesn't cause issues while playing When reloading the world, Minecraft is unable to read (parse) this biome data

Add the new crash-report or log

Make a test without the mod bettervillage

Looks like the Launcher does not have perms for the /home/botfly/ directory So you have to grant permission for /home/botfly/.minecraft/ But I have no idea how this work on linux

It is a rendering mod - so start with embeddium/oculus

Also make a test without the mod auroras

Make a test without the mod amendments

Also try older builds of bclib and moonlight lib

Looks more like a conflict with entity_model_features - make a test without it or try an older build

Did you check the RAM allocation? Change it to 6 GB if 4 GB are still set

Are there changes, if you set max-tick-time to -1 in the server.properties?