I use a multitude of mods (~80). I tried adding replay mod "replaymod-1.20.2-2.6.14" to my list of mods and the game crashed during bootup. I compartmentalized and found that the Item Swapper mod "itemswapper-fabric-0.5.4-mc1.20.2" and the replay mod cause a crash when they are both in my mods folder.

Link to the Item Swapper Modrinth page: https://modrinth.com/plugin/itemswapper

Please attach the log file (.minecraft/logs/latest.log) that contains the crash.

latest.log

You're using an old version of itemswapper, this has been fixed in version 0.5.5: tr7zw/ItemSwapper#187

ReplayMod includes some parts of fabric-api 0.91.2, hence why it breaks when you add it.

Just tested and it works, thank you!