I followed the suggestion on github and added the following line: "option compat_version '1.1'" to /etc/config/system. Afterwards I was able to run the upgrade from CLI.
However, after the "upgrade" was completed, the version that is shown in openwrt is much older than the one I was upgrading from.. Actually, it downgraded the version from r22767 to r21629.
I've tried running the upgrade with -n and even tried upgrading to the recent stable release (from Nov 15, 2023) - but the firmware is stuck on version r21629.
I suspect there is some kind of a "recovery partition" which contains an old version, which for some reason "kidnapped" my device... if not that, I'm probably going crazy
Actually, my plan was to upgrade to a stable release, but as a last-minute decision, I decided going with a snapshot.. probably I should have installed a stable release.
So the answer is "no", there is no any special reason for me to install a snapshot.
However, as I mentioned above, I did try installing a stable release after I tried installing a snapshot, but the openwrt firmware remained r21629
It is worth mentioning, that after the installation of the snapshot version, I tried updating it with "opkg update" but received the following error:
Ok, just wanted to update that the solution was reinstalling openwrt from scratch on the device (SD--> NAND --> EMMC). So now I'm running a stable release (r23630 - 23.05.2).