I did an upgrade from
OpenWrt 21.02.0-rc1, r16046-59980f7aa
OpenWrt 21.02.0, r16279-5cc0535800
It looks like it kept the settings, but the 3rd LED (WLAN) from left is blinking. but I am connected via Wifi.
It is a wireless bridge client and I can access via Wifi. Browser works, ssh works.
Another TL-WR1043ND v1 with OpenWrt 21.02.0-rc1 does not blink.
Edit: In the meantime I updated the other too to OpenWrt 21.02.0 and it doesn't blink, but this one has another setup. It are routers for testing, don't know what I tested the last time with it,
LED configurations typically happen in /etc/config/system, compare those files on your devices. There have been changes in the way these are set up (I don't remember if that happened before- or after 19.07.x) and keeping settings might lead to an inconsistent behaviour.