I was trying out your RoundCorners skin with the latest release 2.2.3 on ubuntu 20.20
i copied the files into /usr/share/mixxx/skins/RoundCorners and loaded it in the gui , it flicked and then segfaulted.
heres some of the error messages , i've trimmed the repeating Argument missing errors with various number combos as they all followed pattens.
Warning [Main]: src/skin/legacyskinparser.cpp:2110 SKIN ERROR at skin:tool_bar.xml:344 <Connection>: LegacySkinParser::setupConnections(): EmitOnPressAndRelease must not set false
Warning [Main]: src/skin/legacyskinparser.cpp:2110 SKIN ERROR at skin:skin_settings.xml:40 <Connection>: LegacySkinParser::setupConnections(): EmitOnPressAndRelease must not set false
Warning [Main]: QString::arg: Argument missing: "2" , 28
Warning [Main]: QString::arg: Argument missing: " 3" , 29
Warning [Main]: QString::arg: Argument missing: "3" , 30
Warning [Main]: QString::arg: Argument missing: " 4" , 31
Warning [Main]: QString::arg: Argument missing: "4" , 32
Warning [Main]: QString::arg: Argument missing: " 5" , 33
Warning [Main]: QString::arg: Argument missing: "5" , 34
Warning [Main]: QString::arg: Argument missing: " 6" , 35
Warning [Main]: QString::arg: Argument missing: "6" , 36
Warning [Main]: WARNING: slotNumber out of range
Warning [Main]: EffectPushButton "[QuickEffectRack1_[Channel1]_Effect1]" , "enabled" is not an effect button parameter.
Warning [Main]: WARNING: slotNumber out of range
Warning [Main]: EffectPushButton "[QuickEffectRack1_[Channel2]_Effect1]" , "enabled" is not an effect button parameter.
Warning [Main]: ControlDoublePrivate::getControl returning NULL for ( "" , "visual_key_distance" )
Warning [Main]: QString::arg: Argument missing: " 1 " , 1
Warning [Main]: QString::arg: Argument missing: " 2 " , 2
Warning [Main]: QString::arg: Argument missing: " 3 " , 3
Warning [Main]: QString::arg: Argument missing: " 6" , 35
Warning [Main]: QString::arg: Argument missing: "6" , 36
Warning [Main]: ControlDoublePrivate::getControl returning NULL for ( "" , "visual_key_distance" )
Warning [Main]: QString::arg: Argument missing: " 1 " , 1
Warning [Main]: QString::arg: Argument missing: " 2 " , 2
Warning [Main]: QString::arg: Argument missing: " 5" , 33
Warning [Main]: QString::arg: Argument missing: "5" , 34
Warning [Main]: QString::arg: Argument missing: " 6" , 35
Warning [Main]: QString::arg: Argument missing: "6" , 36
Warning [Main]: WARNING: slotNumber out of range
Warning [Main]: EffectPushButton "[QuickEffectRack1_[Channel3]_Effect1]" , "enabled" is not an effect button parameter.
Warning [Main]: WARNING: slotNumber out of range
Warning [Main]: EffectPushButton "[QuickEffectRack1_[Channel4]_Effect1]" , "enabled" is not an effect button parameter.
Warning [Main]: ControlDoublePrivate::getControl returning NULL for ( "" , "visual_key_distance" )
Warning [Main]: QString::arg: Argument missing: " 1 " , 1
Warning [Main]: QString::arg: Argument missing: " 2 " , 2
Warning [Main]: QString::arg: Argument missing: " 3 " , 3
Does it just not work with the release version yet ? happy to help test fixes or workarounds