My understanding from the "official" timeline of OpenWrt, is that 21.02 is still supported for security updates until April 2023: https://openwrt.org/about/history#openwrt_2102
I went ahead and moved to the latest 21.02 because I don't want to be dealing with snapshot installs and checking back every week or so on the forums to see if I should again update to the most current snapshot or not. It seems that as long as OpenWrt does follow their own maintenance timelines, going to 21.02 is perfectly safe until April 2023 (and my impression that this is recommended over staying in 22.03.2 in the affected devices, since those no longer will receive security updates).
Edit: And hopefully, v23 comes out before April 2023...