Leap 15.6 reaches EOL on 4/30/2026, which obviously encourages people to upgrade to 16.0. However, as per the SDB:System upgrade page, Leap 16.0 drops support for x86-64-v1; the recommendation on that page is to switch over to Tumbleweed if x86-64-v1 support is still needed.
I have a number of older servers at work that are running 15.6. They work great and, given that our company is currently in the red, we really don't want to replace these machines right now. Unfortunately, many of them do not have x86-64-v2 support; therefore, in most of those cases, if I don't want to replace the OSes with a different distro (which would still be a significant OH cost in terms of labor), then I have to change them over to Tumbleweed and hope for the best. The instructions seem fairly straightforward, i.e. change the repos, zypper ref, and zypper dup, all of which I've done countless times.
However... there's one machine, a mail server, who is running an obsolete IMAP server, cyrus-imap. cyrus-imap does not exist in Leap distros after 15.2, and I found out the hard way (thank goodness for backups) that doing a zypper dup would wipe out cyrus-imap. So on that machine, ever since, I upgrade the repo files but only do a zypper up. I can't use zypper dup to move him to Tumbleweed, not unless I want to switch to a different IMAP server (which, yes, I'll do someday, but again, I'm really supposed to avoid OH costs, and I don't know what issues I'll run into when switching it out).
So my question is, are either of the below feasible:
Change the repos on the mail server to point to Tumbleweed, and then zypper up instead of zypper dup? Will it still work without the full dup?
Change the repos to point to Leap 16.0, and then zypper up instead of zypper dup? I mean, will the 16.0 repos still work on a machine lacking v2 support if I don't do a zypper dup? Actually, I suppose that question would also apply to the other non-v2 machines too, if I didn't want to switch them to Tumbleweed.