We also have most of the route open in Cumbria and also in a large part of Lancashire. In Cumbria it is open from the Scottish Border to Millom then Barrow in Furness to the Lancashire border. There are a few bridge crossings over rivers to build so there are 3 sections currently where you have to nip onto the train at those points. I keep doing the Cumbrian bits as and when they open.
The other ultra long distance route in the UK is the Trans Pennine Trail. That is a very small part of the E8 European walking route from Cork to Turkey. That is said to be 2920 miles. Not sure if that is 2920 walking miles or includes the two sea crossings.
On the continent it crosses the Netherlands, Germany, Austria, Slovakia, Poland, Ukraine, Romania, Bulgaria and Turkey. Probably impossible to do currently due to the war.
It is one of 12 designated long distance walks across Europe.