It seems like this comes from the update yesterday. Have an up-to-date version, but without the mentioned patch.
$ wine drive_c/Program\ Files/Wizards\ of\ the\ Coast/MTGA/MtgaLauncher.exe
000b:fixme:thread:create_user_shared_data_thread Creating user shared data update thread.
000b:fixme:winediag:start_process Wine Staging 4.12.1 is a testing version containing experimental patches.
000b:fixme:winediag:start_process Please mention your exact version when filing bug reports on winehq.org.
000f:fixme:thread:create_user_shared_data_thread Creating user shared data update thread.
000d:fixme:thread:create_user_shared_data_thread Creating user shared data update thread.
0014:fixme:thread:create_user_shared_data_thread Creating user shared data update thread.
0012:fixme:thread:create_user_shared_data_thread Creating user shared data update thread.
0012:err:winediag:xrandr12_init_modes Broken NVIDIA RandR detected, falling back to RandR 1.0. Please consider using the Nouveau driver instead.
001c:fixme:thread:create_user_shared_data_thread Creating user shared data update thread.
0021:fixme:thread:create_user_shared_data_thread Creating user shared data update thread.
000b:err:winediag:xrandr12_init_modes Broken NVIDIA RandR detected, falling back to RandR 1.0. Please consider using the Nouveau driver instead.
000d:err:winediag:xrandr12_init_modes Broken NVIDIA RandR detected, falling back to RandR 1.0. Please consider using the Nouveau driver instead.
0009:fixme:ntdll:EtwEventRegister ({319dc449-ada5-50f7-428e-957db6791668}, 0x10023780, 0x10071b20, 0x10071b38) stub.
0009:fixme:ntdll:EtwEventSetInformation (deadbeef, 2, 0x10003109, 28) stub
0009:fixme:reg:GetEnabledXStateFeatures
0009:fixme:ntdll:EtwEventRegister ({319dc449-ada5-50f7-428e-957db6791668}, 0x931d60, 0xdd1048, 0xdd1060) stub.
0009:fixme:ntdll:EtwEventSetInformation (deadbeef, 2, 0x76060d, 28) stub
0009:fixme:kernelbase:QuirkIsEnabled3 (0034F508, FFFFFFFF) stub!
0009:fixme:process:GetNumaHighestNodeNumber (0x34fc3c): semi-stub
0009:fixme:thread:SetThreadStackGuarantee (0x34fc2c): stub
0009:fixme:ntdll:EtwEventRegister ({e13c0d23-ccbc-4e12-931b-d9cc2eee27e4}, 0xa3b9f0, 0xdd10b8, 0xddcb50) stub.
0009:fixme:ntdll:EtwEventRegister ({763fd754-7086-4dfe-95eb-c01a46faf4ca}, 0xa3b9f0, 0xdd13c8, 0xdd1540) stub.
0009:fixme:ntdll:EtwEventRegister ({a669021c-c450-4609-a035-5af59af4df18}, 0xa3b9f0, 0xddb840, 0xddcb60) stub.
0009:fixme:ntdll:EtwEventRegister ({cc2bcbba-16b6-4cf3-8990-d74c2e8af500}, 0xa3b9f0, 0xdd1210, 0xdd1288) stub.
0009:fixme:wer:WerRegisterRuntimeExceptionModule (L"C:\windows\Microsoft.NET\Framework\v4.0.30319\mscordacwks.dll", 0x750000) stub!
0009:fixme:reg:GetEnabledXStateFeatures
0009:fixme:path:parse_url failed to parse L"System.Net.Http.WebRequest"
0009:fixme:path:parse_url failed to parse L"System.Net.Http"
0009:fixme:path:parse_url failed to parse L"System"
0009:fixme:path:parse_url failed to parse L"System.Configuration"
0009:fixme:path:parse_url failed to parse L"System.Xml"
0009:fixme:path:parse_url failed to parse L"INIFileParser"
0009:fixme:nls:LocaleNameToLCID unsupported flags 8000000
0009:fixme:nls:LCIDToLocaleName unsupported flags 8000000
0009:fixme:nls:get_dummy_preferred_ui_language (0x8 0x34cc5c (nil) 0x34cc58) returning a dummy value (current locale)
0009:fixme:nls:get_dummy_preferred_ui_language (0x8 0x34cc5c 0x14f8b0 0x34cc58) returning a dummy value (current locale)
0009:fixme:path:parse_url failed to parse L"System.Configuration"
0009:fixme:path:parse_url failed to parse L"System.Security"
0009:fixme:path:parse_url failed to parse L"System.Core"
0009:fixme:path:parse_url failed to parse L"System.Numerics"
0009:fixme:path:parse_url failed to parse L"System.Core"
0009:fixme:path:parse_url failed to parse L"System.Xml"
0009:fixme:path:parse_url failed to parse L"System.Data.SqlXml"
0009:err:winediag:xrandr12_init_modes Broken NVIDIA RandR detected, falling back to RandR 1.0. Please consider using the Nouveau driver instead.
0009:fixme:bcrypt:BCryptGetFipsAlgorithmMode 0x34cf54 - semi-stub
0009:fixme:path:parse_url failed to parse L"System"
0009:fixme:nls:GetFileMUIPath stub: 0x10, L"C:\windows\system32\tzres.dll", (null), 0x34f1a0, 0x1e6538, 0x34f1a4, 0x34f198
0009:fixme:nls:GetFileMUIPath stub: 0x10, L"C:\windows\system32\tzres.dll", (null), 0x34f1a0, 0x1e6538, 0x34f1a4, 0x34f198
0009:fixme:path:parse_url failed to parse L"PresentationFramework"
0009:fixme:path:parse_url failed to parse L"WindowsBase"
0009:fixme:path:parse_url failed to parse L"System.Xaml"
0009:fixme:path:parse_url failed to parse L"Accessibility"
0009:fixme:path:parse_url failed to parse L"PresentationCore"
0009:fixme:path:parse_url failed to parse L"UIAutomationTypes"
0009:fixme:path:parse_url failed to parse L"System.Windows.Input.Manipulations"
0009:fixme:path:parse_url failed to parse L"UIAutomationProvider"
0009:fixme:path:parse_url failed to parse L"System.Deployment"
0009:fixme:path:parse_url failed to parse L"ReachFramework"
0009:fixme:path:parse_url failed to parse L"PresentationUI"
0009:fixme:path:parse_url failed to parse L"System.Printing"
0009:fixme:path:parse_url failed to parse L"WindowsBase"
0009:fixme:path:parse_url failed to parse L"PresentationCore"
0009:fixme:reg:GetEnabledXStateFeatures
0009:fixme:ntdll:EtwEventRegister ({e13b77a8-14b6-11de-8069-001b212b5009}, 0x56a28b0, 0x574d008, 0x5752960) stub.
0009:fixme:ntdll:EtwEventRegister ({8e9f5090-2d75-4d03-8a81-e5afbf85daf1}, 0x49505a6, (nil), 0x12d4cfc) stub.
0009:fixme:ver:GetCurrentPackageId (0x34d4c0 (nil)): stub
0009:fixme:ras:RasEnumConnectionsW (00201D48,0034F05C,0034F060),stub!
0009:fixme:ras:RasEnumConnectionsW RAS support is not implemented! Configure program to use LAN connection/winsock instead!
0009:err:winsock:WSAIoctl -> SIO_ADDRESS_LIST_CHANGE request failed with status 0x2733
0009:err:winsock:WSAIoctl -> SIO_ADDRESS_LIST_CHANGE request failed with status 0x2733
0009:fixme:ras:RasConnectionNotificationW (FFFFFFFF,000001EC,0x00000003),stub!
0009:fixme:nls:LCMapStringEx unsupported lparam 1623a8
0009:fixme:ntdll:EtwEventRegister ({38ed3633-5e3f-5989-bf25-f0b1b3318c9b}, 0x495069e, (nil), 0x12f2e1c) stub.
0009:fixme:ntdll:EtwEventSetInformation (deadbeef, 2, 0x12f2ddc, 53) stub
0009:fixme:combase:RoGetActivationFactory (L"Windows.Foundation.Diagnostics.AsyncCausalityTracer", {50850b26-267e-451b-a890-ab6a370245ee}, 0034E9D8): semi-stub
0009:err:combase:RoGetActivationFactory Failed to find library for L"Windows.Foundation.Diagnostics.AsyncCausalityTracer"
0009:fixme:ntdll:EtwEventRegister ({2e5dba47-a3d2-4d16-8ee0-6671ffdcd7b5}, 0x49506c6, (nil), 0x12f4214) stub.
0009:fixme:ntdll:EtwEventSetInformation (deadbeef, 2, 0x12f41e4, 40) stub
0031:fixme:sync:SetWaitableTimerEx (00000214, 05CDFEA0, 500, 00000000, 00000000, 00000000, 50) semi-stub
0030:fixme:winhttp:get_system_proxy_autoconfig_url no support on this platform
0030:fixme:winhttp:WinHttpDetectAutoProxyConfigUrl discovery via DHCP not supported
0030:fixme:winsock:convert_aiflag_w2u Unhandled windows AI_xxx flags 0x20000
0030:err:winsock:WSAIoctl -> SIO_ADDRESS_LIST_CHANGE request failed with status 0x2733
0030:err:winsock:WSAIoctl -> SIO_ADDRESS_LIST_CHANGE request failed with status 0x2733
0030:fixme:ntdll:EtwEventRegister ({6906e6e1-f9cd-5b3b-c846-27578fd8d69e}, 0x49506ee, (nil), 0x1304ef8) stub.
0030:fixme:ntdll:EtwEventSetInformation (deadbeef, 2, 0x1304ec0, 46) stub
0030:fixme:process:FlushProcessWriteBuffers : stub
002e:fixme:ntdll:EtwEventUnregister (deadbeef) stub.
002e:fixme:ntdll:EtwEventUnregister (deadbeef) stub.
002e:fixme:ntdll:EtwEventUnregister (deadbeef) stub.
002e:fixme:ntdll:EtwEventUnregister (deadbeef) stub.
002e:fixme:ntdll:EtwEventUnregister (deadbeef) stub.
0009:fixme:ntdll:EtwEventUnregister (deadbeef) stub.
0009:fixme:ntdll:EtwEventUnregister (deadbeef) stub.
AFAIK they changed the MtgaUpdater.exe to a new interface and maybe that’s the problem. Directly calling MtgaLauncher.exe also gives the following error message: https://i.imgur.com/wQeRck4.png
I don’t have a solution for this, but hopefully this helps for another one here who has an idea!