I use a linksys 1200ac and i always upgraded without any problem, update then restore my backup, always worked like a charm, but now not anymore.
Upgrading to the newer version i cannot use my backup, otherwise nothing working, i don't even get an ip.
I've tryed to setup everything again, but i discovered the "switch" menu isn't there anymore, so i cannot replicate the same setup i had before.
Keep in mind, i'm a noob, i've dedicated a lot of time few years ago to setup everything properly, then every update went smooth, so the need to try to find another solution without the switch it's out of the table (i don't really have enough free time now due to the job)
So i'm here to ask, if the switch menu will be restored in the future, but more important, if will be a chance to have a current backup working on a future version, so i could just upload and apply my system backup
The backups from 19.07 and earlier are not compatible with 21.02 on devices that have migrated from swconfig to DSA (as @anomeome referenced).
Reset your router to defaults and configure from scratch. The /etc/config/network file is the one that is most affected. Some of the other files may be okay, depending on what they are (the firewall and DHCP files should be fine to copy over in most cases).
You need to reconfigure /etc/config/network from scratch due to the switch config change (DSA instead of swconfig), and /etc/config/system due to the network LED changes related to the DSA change. Other normal/common 19.07 config files should be ok with 21.02 (firewall, dhcp, etc.).
Two (semi-)quick dirty solutions for you:
unpack the backup tar.gz archive manually with tar in 21.02, and copy all other config files to /etc/config but NOT network and system.
sysupgrade back to 19.07 (or simply switch boot partition to be the old 19.07 that you still have as the fallback alternative, right? In 19.07, remove the /etc/config/network and /etc/config/system files.
Then sysupgrade to 21.02 (keeping other settings, but having deleted network and system files).
OpenWrt will generate new DSA defaults for those two config files at the reboot after the flashing, if those two files are missing.
In both cases, you need to reconfigure network with the DSA approach, like said above. No way to avoid that.
Inside the tar.gz i have different folders, should i copy online the config without network and system or i also have to copy other folders/files too? If yes should i copy them under /etc/ ?
With the older method i've assigned 2 eth port the same interface, while the eth port 1 and 4 they have a different interface each.
There is a solution with luci, to achieve the same results? (i was using "switch" for doing that)