I think this is the same issue as here? https://forum.quiltmc.org/t/dynmap-crashes-quilt-but-works-on-fabric/635
Call stack trace:
java.lang.UnsupportedOperationException: Only the default FileSystem supports 'Path.toFile()', class org.quiltmc.loader.impl.filesystem.QuiltZipPath '/' does not!
at org.quiltmc.loader.impl.filesystem.QuiltBasePath.toFile(QuiltBasePath.java:511) ~[quilt-loader-0.19.1.jar:?]
at org.dynmap.fabric_1_20.FabricServer.getModContainerFile(FabricServer.java:548) ~[transformed-mod-dynmap-v3.6-beta-2.jar:?]
at org.dynmap.hdmap.HDBlockModels.loadModels(HDBlockModels.java:194) ~[transformed-mod-dynmap-v3.6-beta-2.jar:?]
at org.dynmap.DynmapCore.enableCore(DynmapCore.java:595) ~[transformed-mod-dynmap-v3.6-beta-2.jar:?]
at org.dynmap.fabric_1_20.DynmapPlugin.onStart(DynmapPlugin.java:457) ~[transformed-mod-dynmap-v3.6-beta-2.jar:?]
at org.dynmap.fabric_1_20.DynmapPlugin.serverStarted(DynmapPlugin.java:241) ~[transformed-mod-dynmap-v3.6-beta-2.jar:?]
at org.dynmap.fabric_1_20.event.CustomServerLifecycleEvents.lambda$static$0(CustomServerLifecycleEvents.java:11) ~[transformed-mod-dynmap-v3.6-beta-2.jar:?]
at net.minecraft.server.MinecraftServer.handler$zbf000$dynmap$loadWorld(MinecraftServer.java:1803) ~[transformed-mod-minecraft.i0:0/:?]
at net.minecraft.server.MinecraftServer.method_3735(MinecraftServer.java) ~[transformed-mod-minecraft.i0:0/:?]
at net.minecraft.class_3176.method_3823(class_3176.java:169) ~[transformed-mod-minecraft.i0:0/:?]
at net.minecraft.server.MinecraftServer.method_29741(MinecraftServer.java:646) ~[transformed-mod-minecraft.i0:0/:?]
at net.minecraft.server.MinecraftServer.method_29739(MinecraftServer.java:265) ~[transformed-mod-minecraft.i0:0/:?]
at java.lang.Thread.run(Thread.java:1623) ~[?:?]