This may be similar to closed issue #1068. But I think it is different. After building the deb package and during the install there are two errors and a lot of suggestions.

Error 1: the file 00fink-vars.el needs to be updated to handle the version 26 changes in syntax. I don't think I saw this when installing emacs25.

in fink-file->string:
opt/sw/etc/emacs26/site-start.d/00fink-vars.el:32:23:Warning: Use
`with-current-buffer' rather than save-excursion+set-buffer

Error 2: Suggestion for updating the fink-startup.el file for changes in syntax.

In fink-run-directories:
opt/sw/share/emacs26/site-lisp/fink-startup.el:131:49:Warning: mapcar' called for effect; use mapc' or `dolist' instead

Not sure if these are fatal flaws nor am I an elisp hacker to try to fix those.

The other issue is a bit curious The message is:

The package emacs26-nox should be rebuilt with new debhelper to get trigger support
Ignoring install-info called from maintainer script

Now debhelper is a fink package but not required for the build process but required for the install process? There is no "InstallDeps" tag AFAIK in the fink universe. Debhelper is current version 12.7.1.