By Matt Hughes Manchester United have opened talks with the Rugby Football League over a long-term deal to host the Super League Grand Final at Old Trafford – the clearest hint yet that they are pressing ahead with plans to build a new 100,000 stadium next door. The RFL’s current staging agreement with United expires following next month’s Super League season finale, with Old Trafford having hosted all but one of the 26 previous Grand Finals. The 2020 final was moved to Hull’s KC Stadium by the RFL to cut costs when fans were banned during the second Covid lockdown. RFL executives are understo…