@jonasschnelli wrote in #14979:
> #14573 broke < Qt5.6 compatibility due to calling the lambda version of `addAction` that was added in Qt5.6.

We currently [support](https://github.com/bitcoin/bitcoin/blob/master/doc/dependencies.md) QT >=5.2, but hardly anyone tests with that. If we make one of the Travis machines use it, we should have a better change of catching this.

See also discussion about minimum QT version in #13478 
if (nMaxVersion == 0) 
        {
            walletInstance->WalletLogPrintf("Performing wallet upgrade to %i\n", FEATURE_LATEST);
            nMaxVersion = FEATURE_LATEST;
            walletInstance->SetMinVersion(FEATURE_LATEST); 
        }
        else
            walletInstance->WalletLogPrintf("Allowing wallet upgrade up to %i\n", nMaxVersion);
        if (nMaxVersion < walletInstance->GetVersion())
        {
            InitError(_("Cannot downgrade wallet"));
            return nullptr;
        }
        walletInstance->SetMaxVersion(nMaxVersion);
    }
    
    if (gArgs.GetBoolArg("-upgradewallet", false)) {
        LOCK(walletInstance->cs_wallet);
        
        int max_version = walletInstance->nWalletVersion;
        if (!walletInstance->CanSupportFeature(FEATURE_HD_SPLIT) && max_version >=FEATURE_HD_SPLIT && max_version < FEATURE_PRE_SPLIT_KEYPOOL) {
            InitError(_("Cannot upgrade a non HD split wallet without upgrading to support pre split keypool. Please use -upgradewallet=169900 or -upgradewallet with no version specified."));
            return nullptr;
        }
        bool hd_upgrade = false;
        bool split_upgrade = false;
        if (walletInstance->CanSupportFeature(FEATURE_HD) && !walletInstance->IsHDEnabled()) {
            walletInstance->WalletLogPrintf("Upgrading wallet to HD\n");
            walletInstance->SetMinVersion(FEATURE_HD);