Afternoon , personally from many years experience in the motor trade the only real repair is to replace the seals . At a push you can glue the cracks together using proper isocyanate glue & not the junk sold in pound shops .
However for a nice job , you can buy universal door seal by the meter or try this firm
https://transport.albertjagger.co.uk...aling-profiles or these
https://www.vikingextrusions.co.uk/p...ubber-profiles or even these folks
https://www.par-group.co.uk/ . Repaired seals usually look like junk , leak anyway & tend to be noisy