Thx4 your support! I gave up on fixing the old install and started over with brand new install of OH2.4: All was up&running in 45mins!! MQTT2.4 with embedded broker works like a charm. On top the Mysensors MQTT GW Ting was online with 1-click! All my MYsensor nodes where recognized immediately! What a relief!
Hope someone will update Mysensors docu so others will be spared the pain...