Well, I came across this article. It do not contains full list of phones supporting both 802.11k and 802.11r. By testing, I found out that A40, A51 and A02s supports wifi roaming, but A41 and A12 not... For me, it seems like phones with Snapdragon has support, MediaTek lack support
Good point, thank you. Both A40 and A51 have Exynos and wifi roaming is working as expected. A02 has two versions, one with Mediatek, one with Snapdragon:
https://www.gsmarena.com/samsung_galaxy_a02s-10603.php - wifi roaming tested and working
So the problem with wifi roaming is only with Mediatek chipsets?