The Exynos variants of Samsung devices can have their bootloader unlocked, it’s the snapdragon ones that can’t and even then there are some instances where it was possible to do it, but it’s still a hassle and the Exynos variants tend not to have good development support.
I bought a second hand pixel 6a a couple weeks ago, my previous phone was the OnePlus 3, lasted me 5 years and at the time of purchase it was already a two years old second hand, bought them for basically the same price, 200€.