Few weeks edit; new pictures attached. I recognise it but plantnet didn’t seem very confident
Coming up in my garden right next to some forest (primarily oak mixed with beech, birch, maple) in southwest Sweden. Last year i dug the area out and removed (most) roots. Not much came up but this little sprout. I suppose it could be roots reaching in from the adjacent forest.
I say let it grow and find out. Bamboo isn’t some kind of unkillable super monster, no harm to leave it in case it’s a pretty flower.