the firmware selector proposes all versions 21.02 for my linksys WRT1900AC v2, but the 1900AC page still recommends 19.07.7. Can you advise if the 21.02 is fine for my router. system works much better since i installed openwrt i don't want to take risks
The wiki will only be updated (in bulk) after 21.02.0 has been released, that hasn't happened yet (we're at 21.02.0-rc3, in the release candidate phase). In general, the RCs should be fine (and if they aren't tested by users, potential (reported-) issues will never be found nor fixed before final either), but the DSA changes are quite invasive (read about it first).
thank you again. "image version mismatch / image check" i understand that i will have to force the image to be installed and reconfigure all settings including ppoe, wireless etc.?
There is a post in one of the 21.02rc? threads that indicates apparently only the system and network files need to change in /etc/config/. Perhaps through an unrelated error I introduced without realizing it, but I was not able to copy backups of my other files (firewall, wireless, etc.) into /etc/config/ and get everything working. So this is why I suggest safest approach is to just start over from scratch.
Unless there are (non-default) private VLAN configurations currently configured (you'd know, if there are), that thread won't be necessary - the defaults work (LAN side, WAN/ PPPoE needs to be reconfigured by hand, just like anything else) via 192.168.1.1.