I checked logcat – the issue appears to be the same as this issue reported a while ago in Graphene OS (eSIM activation fails from multiple carrier apps · Issue #3794 · GrapheneOS/os-issue-tracker · GitHub): the app waits for a confirmation popup from OpenEUICC, which is not allowed to be triggered by the esim-carrier app, and thus never appears on screen.
03-16 12:54:07.252 1438 12211 D CoreBackPreview: Window{3f6a8a9 u0 nl.simyo.mijnsimyo/nl.simyo.mijnsimyo.flutter.view.FlutterFullScreenActivity}: Setting back callback OnBackInvokedCallbackInfo{mCallback=android.window.IOnBackInvokedCallback$Stub$Proxy@f4f3678, mPriority=0, mIsAnimationCallback=true, mOverrideBehavior=0}
03-16 12:54:08.322 14293 14293 D FLUTTER ESIM DEBUG: DOWNLOADING SUBSCRIPTION...
03-16 12:54:08.323 14293 14293 D FLUTTER ESIM DEBUG: SWITCH AFTER DOWNLOAD true
03-16 12:54:08.326 14293 14293 D FLUTTER ESIM DEBUG: DOWNLOADING SUBSCRIPTION...ANDROID 12 CHECK
03-16 12:54:08.326 14293 14293 D FLUTTER ESIM DEBUG: new version
03-16 12:54:08.327 14293 14293 D FLUTTER ESIM DEBUG: DOWNLOADING SUBSCRIPTION...STARTING REQUEST
03-16 12:54:08.333 2729 3108 I EuiccController: isCompatChangeEnabled changeId: 224562872 changeEnabled: true
03-16 12:54:08.337 2729 3108 D EuiccController: Multiple enabled profiles is not supported, return default port index
03-16 12:54:08.337 2729 3108 D EuiccController: downloadSubscription cardId: 0 switchAfterDownload: true portIndex: 0 forceDeactivateSim: false callingPackage: nl.simyo.mijnsimyo isConsentNeededToResolvePortIndex: false shouldResolvePortIndex:true callerHasAdminPrivileges:false
03-16 12:54:08.338 2729 3108 I EuiccController: Caller can't manage subscription on target SIM or User consent is required for resolving port index. Ask user's consent first
03-16 12:54:08.356 14293 14293 D FLUTTER ESIM DEBUG: ON RECEIVE
03-16 12:54:08.356 14293 14293 D : action=download_subscription, resultCode=1, resultData=null, detailedCode=0.
03-16 12:54:08.356 14293 14293 D FLUTTER ESIM DEBUG: RESOLVABLE ERROR
03-16 12:54:08.358 14293 14293 D FLUTTER ESIM DEBUG: resolving error
03-16 12:54:08.364 1438 14281 V WindowManager: DesktopModeLaunchParamsModifier: phase= 0 task=null activity=null desktop mode is not enabled, skipping
03-16 12:54:08.364 1438 14281 V WindowManager: TaskLaunchParamsModifier:phase=0 task=null activity=null display-area-from-source=DefaultTaskDisplayArea@106089900 display-id=0 task-display-area-windowing-mode=1 suggested-display-area=DefaultTaskDisplayArea@106089900
03-16 12:54:08.369 1438 14281 V WindowManager: DesktopModeLaunchParamsModifier: phase= 0 task=null activity=ActivityRecord{200585660 u0 com.android.phone/.euicc.EuiccResolutionUiDispatcherActivity desktop mode is not enabled, skipping
03-16 12:54:08.369 1438 14281 V WindowManager: TaskLaunchParamsModifier:phase=0 task=null activity=ActivityRecord{200585660 u0 com.android.phone/.euicc.EuiccResolutionUiDispatcherActivity t-1} display-area-from-source=DefaultTaskDisplayArea@106089900 display-id=0 task-display-area-windowing-mode=1 suggested-display-area=DefaultTaskDisplayArea@106089900
03-16 12:54:08.370 1438 14281 V WindowManager: DesktopModeLaunchParamsModifier: phase= 3 task=Task{d9186aa #854 type=standard A=10231:nl.simyo.mijnsimyo} activity=ActivityRecord{200585660 u0 com.android.phone/.euicc.EuiccResolutionUiDispatcherActivity t-1} desktop mode is not enabled, skipping
03-16 12:54:08.371 1438 14281 V WindowManager: TaskLaunchParamsModifier:phase=3 task=Task{d9186aa #854 type=standard A=10231:nl.simyo.mijnsimyo} activity=ActivityRecord{200585660 u0 com.android.phone/.euicc.EuiccResolutionUiDispatcherActivity t-1} display-area-from-source=DefaultTaskDisplayArea@106089900 display-id=0 task-display-area-windowing-mode=1 suggested-display-area=DefaultTaskDisplayArea@106089900 inherit-from-source=fullscreen non-freeform-task-display-area display-area=DefaultTaskDisplayArea@106089900 default-portrait freeform-size-mismatch=Rect(314, 763 - 910, 1987)
03-16 12:54:08.372 1438 14281 V WindowManager: DesktopModeLaunchParamsModifier: phase= 3 task=Task{d9186aa #854 type=standard A=10231:nl.simyo.mijnsimyo} activity=ActivityRecord{200585660 u0 com.android.phone/.euicc.EuiccResolutionUiDispatcherActivity t-1} desktop mode is not enabled, skipping
03-16 12:54:08.373 1438 14281 V WindowManager: TaskLaunchParamsModifier:phase=3 task=Task{d9186aa #854 type=standard A=10231:nl.simyo.mijnsimyo} activity=ActivityRecord{200585660 u0 com.android.phone/.euicc.EuiccResolutionUiDispatcherActivity t-1} display-area-from-source=DefaultTaskDisplayArea@106089900 display-id=0 task-display-area-windowing-mode=1 suggested-display-area=DefaultTaskDisplayArea@106089900 inherit-from-source=fullscreen non-freeform-task-display-area display-area=DefaultTaskDisplayArea@106089900 default-portrait freeform-size-mismatch=Rect(314, 763 - 910, 1987)
Reading this GrapheneOS issue, I believe this is an configuration issue in iodeOS, not in OpenEUICC (?).
Can you fix this? Here is the patch that worked for GrapheneOS a while ago: