Ireland is the easiest one and one I’m seriously considering. You can move and work visa free as a UK citizen, and after you’ve lived there for 5 years you can claim Irish citizenship. EU passport back and can go wherever you want. I quite like the Irish craic so I might end up making it home for good.
Handy if you’ve got roots in the UK as well because you’re not far away, especially if you live near Dublin which has flights to most major cities in the UK for £20 to £30. Only problem is they’ve got an even worse housing crisis and cost of living crisis than we do. Significantly more expensive than even Scandinavia.