Yes, the shape of the shorter leaves in the first picture instantly made me think dandelion or sow thistle, but they just don't grow tall like that. If it occured in my garden I would classify it as 'weed' and file carefully in the compost heap.It looks like some kind of thistle weed, like a melancholy thistle but I can't say for sure what it is.
I think your plant could be one of the Tragopodons aka Salsify. There are a few varieties, and more than I know in the USA. We have some very similar looking ones that began to grow here, and believe it seeded from a neighbours garden.
If you leave it and allow it to flower you will know better. The ones that grow here have a flower like this -
View attachment 97733 and a seed head like this View attachment 97734 the first leaves can resemble the dandelion as well as the seed head.
This is a member of the dandelion family, is edible, and more commonly known as the oyster plant.
Of course, I could well be wrong - but it would be interesting to watch it flower to know!
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