I agree and from what I have heard I'm almost certain Foos are doing R+L and struggle to see both bands at R+L in the same year, so realistically the only options for Linkin Park are Isle of Wight, Glastonbury and/or BST.
Isle of Wight pay their headliners the bag, will let them play other shows and is a Live Nation event so is definitely feasible.
BST would allow them to play an outdoors festival show and some additional shows around the UK. Would also mean they could do Glastonbury.
Glastonbury they get loads of exposure and would be allowed to do other shows as most Glastonbury headliners do allow other shows around the UK. Guns 'n' Roses, Elton John and Arctic Monkey's all did in 2023 and rumours were Stevie Wonder was doing Glastonbury and BST until he pulled out of both...
I think BST or Isle of Wight and other shows seems most likely, but if they were discussing festival slots and are certain to be in Europe if Glastonbury was struggling to pick up headliners I could see them approaching them. Would imagine that they would get a decent crowd there as most people will surely know Numb, In the End, What I've Done and Crawling.