Thank you for your reply. I will try to open a support ticket.

If there is anyone wondering what the issue is in the log:

Caught fatal signal - signo:11 code:1 errno:0 addr:0x50

Seems to be related with Unity packaging running on Ubuntu when using mono.
I find this curious. I let anyone knows if I get it fix ( and how of course ).

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Full Log
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Loading in SingleInstance mode
Mono path[0] = '/home/steam/.steam/steamapps/common/Valheim dedicated server/valheim_server_Data/Managed'
Mono config path = '/home/steam/.steam/steamapps/common/Valheim dedicated server/valheim_server_Data/MonoBleedingEdge/etc'
Preloaded 'libsteam_api.so'
Unable to preload the following plugins:
libparty.so
Initialize engine version: 2020.3.33f1 (915a7af8b0d5)
[Subsystems] Discovering subsystems at path /home/steam/.steam/steamapps/common/Valheim dedicated server/valheim_server_Data/UnitySubsystems
Forcing GfxDevice: Null
GfxDevice: creating device client; threaded=0
NullGfxDevice:
Version: NULL 1.0 [1.0]
Renderer: Null Device
Vendor: Unity Technologies
Begin MonoManager ReloadAssembly
- Completed reload, in 0.112 seconds
ERROR: Shader Sprites/Default shader is not supported on this GPU (none of subshaders/fallbacks are suitable)
ERROR: Shader Sprites/Mask shader is not supported on this GPU (none of subshaders/fallbacks are suitable)
ERROR: Shader GUI/Text Shader shader is not supported on this GPU (none of subshaders/fallbacks are suitable)
UnloadTime: 1.158220 ms
Caught fatal signal - signo:11 code:1 errno:0 addr:0x50
Obtained 49 stack frames.
#0 0x007f7cbc1ce8a0 in funlockfile
#1 0x007f7cbe88db18 in _dl_rtld_di_serinfo
#2 0x007f7cbe89610d in _dl_find_dso_for_object
#3 0x007f7cbbf3251f in _dl_catch_exception
#4 0x007f7cbe89581a in _dl_find_dso_for_object
#5 0x007f7cbbbc7f96 in (Unknown)
#6 0x007f7cbbf3251f in _dl_catch_exception
#7 0x007f7cbbf325af in _dl_catch_error
#8 0x007f7cbbbc8745 in dlerror
#9 0x007f7cbbbc8051 in dlopen
#10 0x007f7cbb45f28e in mono_dl_open
#11 0x007f7cbb3daecd in mono_jit_info_get_method
#12 0x007f7cbb3dc017 in mono_lookup_pinvoke_call
#13 0x007f7cbb3eef0c in mono_marshal_string_to_utf16
#14 0x007f7cbb2afa82 in mono_set_break_policy
#15 0x007f7cbb2944a4 in _init
#16 0x007f7cbb295f1c in _init
#17 0x007f7cbb299dfa in mono_print_method_from_ip
#18 0x007f7cbb319bde in mono_print_thread_dump_from_ctx
#19 0x007f7cbb319f0d in mono_print_thread_dump_from_ctx
#20 0x00000040cb8393 in (Unknown)
#21 0x00000040f8bc48 in System.TimeZoneInfo:TryGetNameFromPath (string,string&)
#22 0x00000040f84d18 in System.TimeZoneInfo:get_Local ()
#23 0x007f7cbb29acdd in mono_print_method_from_ip
#24 0x007f7cbb40ab18 in mono_perfcounter_foreach
#25 0x007f7cbb40b9c5 in mono_runtime_invoke
#26 0x007f7cbd84fb62 in scripting_method_invoke(ScriptingMethodPtr, ScriptingObjectPtr, ScriptingArguments&, ScriptingExceptionPtr*, bool)
#27 0x007f7cbd84dc72 in ScriptingInvocation::Invoke(ScriptingExceptionPtr*, bool)
#28 0x007f7cbd82de47 in Coroutine::InvokeMoveNext(ScriptingExceptionPtr*)
#29 0x007f7cbd82da75 in Coroutine::Run(bool*)
#30 0x007f7cbd8311de in MonoBehaviour::TryCreateAndRunCoroutine(ScriptingObjectPtr, ScriptingMethodPtr, Coroutine**)
#31 0x007f7cbd8315b2 in MonoBehaviour::StartCoroutineManaged2(ScriptingObjectPtr)
#32 0x007f7cbd920ffe in MonoBehaviour_CUSTOM_StartCoroutineManaged2(ScriptingBackendNativeObjectPtrOpaque*, ScriptingBackendNativeObjectPtrOpaque*)
#33 0x00000040f8416e in (wrapper managed-to-native) UnityEngine.MonoBehaviour:StartCoroutineManaged2 (UnityEngine.MonoBehaviour,System.Collections.IEnumerator)
#34 0x007f7cbb29acdd in mono_print_method_from_ip
#35 0x007f7cbb40ab18 in mono_perfcounter_foreach
#36 0x007f7cbb40b9c5 in mono_runtime_invoke
#37 0x007f7cbd84fb62 in scripting_method_invoke(ScriptingMethodPtr, ScriptingObjectPtr, ScriptingArguments&, ScriptingExceptionPtr*, bool)
#38 0x007f7cbd84dc72 in ScriptingInvocation::Invoke(ScriptingExceptionPtr*, bool)
#39 0x007f7cbd832201 in MonoBehaviour::InvokeMethodOrCoroutineChecked(ScriptingMethodPtr, ScriptingObjectPtr, ScriptingExceptionPtr*)
#40 0x007f7cbd832322 in MonoBehaviour::InvokeMethodOrCoroutineChecked(ScriptingMethodPtr, ScriptingObjectPtr)
#41 0x007f7cbd832bf6 in MonoBehaviour::DelayedStartCall(Object*, void*)
#42 0x007f7cbd569202 in DelayedCallManager::Update(int)
#43 0x007f7cbd6cf957 in ExecutePlayerLoop(NativePlayerLoopSystem*)
#44 0x007f7cbd6cf912 in ExecutePlayerLoop(NativePlayerLoopSystem*)
#45 0x007f7cbd6cfebe in PlayerLoop()
#46 0x007f7cbd8adbab in PlayerMain(int, char**)
#47 0x007f7cbbdecb97 in __libc_start_main
#48 0x00559e1b860029 in _start
Segmentation fault