Hi.
A suggestion for the website: the download page ... https://downloads.openwrt.org/
provides links to the current stable (19.07.7) and next stable (21.02.rc1), master snapshots, and archived releases. What about also linking to 19.07 and 21.02 snapshots ? Without knowing the dir url, the only way to get these snapshots is to use the firmware selector.
I agree that the links to the active snapshots should be visible, they are there anyway but invisible from the download page. https://downloads.openwrt.org/releases/21.02-SNAPSHOT/ (change 21.02 to 19.07 in the address to get the 19.07 snapshot)
The 19.07.6 was a pretty messed up version with dnsmasq so it is maybe good it is unavailable, 19.07.7 is in practical terms a 19.07.6 but with a actual working dnsmasq.
I have tested a lot of 21.02 snapshots back in march/april. I used the firmware selector to get a couple of them, than I quickly copied the url to link directly. There is an equal interest to have the master and the 21.02 snapshots available in the download page. Also for 19.07, even if it will end this year.
19.07.6 : agreed. Just put an info message instead of dead links.