> I'm on the focal version of devscripts 2.20.2ubuntu2
> Trying 2.21.1ubuntu1 in Impish ...

Ok, that is it ...
I guess for the MIR we can keep it as is, still slightly sad that it
fails with the uscan of the latest LTS.
I mean it isn't a new format version that would only be supported in
the new one, just behavior of the same rules is different.

FYI

New uscan in impish

root@i:~/libmanette-0.2.6# uscan  --no-download --verbose
uscan info: uscan (version 2.21.1ubuntu1) See uscan(1) for help
uscan info: Scan watch files in .
uscan info: Check debian/watch and debian/changelog in .
uscan info: package="libmanette" version="0.2.6-2" (as seen in debian/changelog)
uscan info: package="libmanette" version="0.2.6" (no epoch/revision)
uscan info: ./debian/changelog sets package="libmanette" version="0.2.6"
uscan info: Process watch file at: debian/watch
    package = libmanette
    version = 0.2.6
    pkg_dir = .
uscan info: Last orig.tar.* tarball version (from debian/changelog): 0.2.6
uscan info: Last orig.tar.* tarball version (dversionmangled): 0.2.6
uscan info: dir=>/sources/libmanette/  dirpattern=>([0-9.]+)
uscan info: Requesting URL:
   https://download.gnome.org/sources/libmanette/
uscan info: Matching pattern:

uscan info: Found the following matching directories (newest first):
   https://download.gnome.org/sources/libmanette/0.2/ (0.2)
   https://download.gnome.org/sources/libmanette/0.1/ (0.1)
uscan info: newest_dir => '0.2'
uscan info: Requesting URL:
   https://download.gnome.org/sources/libmanette/0.2/
uscan info: Matching pattern:
   (?:(?:https://download.gnome.org)?\/sources\/libmanette\/0\.2\/)?libmanette(?:[-_]?(\d[\-+\.:\~\da-zA-Z]*))\.tar\.xz
uscan info: Found the following matching hrefs on the web page (newest first):
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.6.tar.xz
(0.2.6) index=0.2.6-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.6.tar.xz
(0.2.6) index=0.2.6-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.5.tar.xz
(0.2.5) index=0.2.5-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.5.tar.xz
(0.2.5) index=0.2.5-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.4.tar.xz
(0.2.4) index=0.2.4-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.4.tar.xz
(0.2.4) index=0.2.4-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.3.tar.xz
(0.2.3) index=0.2.3-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.3.tar.xz
(0.2.3) index=0.2.3-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.2.tar.xz
(0.2.2) index=0.2.2-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.2.tar.xz
(0.2.2) index=0.2.2-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.1.tar.xz
(0.2.1) index=0.2.1-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.1.tar.xz
(0.2.1) index=0.2.1-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.0.tar.xz
(0.2.0) index=0.2.0-4
   https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.0.tar.xz
(0.2.0) index=0.2.0-4
uscan info: Looking at $base =
https://download.gnome.org/sources/libmanette/0.2/ with
    $filepattern = libmanette(?:[-_]?(\d[\-+\.:\~\da-zA-Z]*))\.tar\.xz found
    $newfile     =
https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.6.tar.xz
    $newversion  = 0.2.6
    $lastversion = 0.2.6
uscan info: Matching target for downloadurlmangle:
https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.6.tar.xz
uscan info: Upstream URL(+tag) to download is identified as
https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.6.tar.xz
uscan info: Filename (filenamemangled) for downloaded file:
libmanette-0.2.6.tar.xz
uscan info: Newest version of libmanette on remote site is 0.2.6,
local version is 0.2.6
uscan info:  => Package is up to date from:
             =>
https://download.gnome.org/sources/libmanette/0.2/libmanette-0.2.6.tar.xz
uscan info: Scan finished


Focals uscan

$ uscan  --no-download --verbose
uscan info: uscan (version 2.20.2ubuntu2) See uscan(1) for help
uscan info: Scan watch files in .
uscan info: Check debian/watch and debian/changelog in .
uscan info: package="libmanette" version="0.2.6-2" (as seen in debian/changelog)
uscan info: package="libmanette" version="0.2.6" (no epoch/revision)
uscan info: ./debian/changelog sets package="libmanette" version="0.2.6"
uscan info: Process watch file at: debian/watch
    package = libmanette
    version = 0.2.6
    pkg_dir = .
uscan info: Last orig.tar.* tarball version (from debian/changelog): 0.2.6
uscan info: Last orig.tar.* tarball version (dversionmangled): 0.2.6
uscan info: dir=>/sources/libmanette/  dirpattern=>([0-9.]+)
uscan info: Requesting URL:
   https://download.gnome.org/sources/libmanette/
uscan info: Matching pattern:
   (?:(?:https://download.gnome.org)?\/sources\/libmanette\/)?([0-9.]+)
uscan info: Matching target for dirversionmangle:   ?C=N&O=A
uscan info: Matching target for dirversionmangle:   ?C=N&O=D
uscan info: Matching target for dirversionmangle:   ?C=S&O=A
uscan info: Matching target for dirversionmangle:   ?C=S&O=D
uscan info: Matching target for dirversionmangle:   ?C=M&O=A
uscan info: Matching target for dirversionmangle:   ?C=M&O=D
uscan info: Matching target for dirversionmangle:   ../
uscan info: Matching target for dirversionmangle:   0.1/
uscan info: Matching target for dirversionmangle:   0.2/
uscan info: Matching target for dirversionmangle:   cache.json
uscan info: Found the following matching directories (newest first):
   ../ (..)
   0.2/ (0.2)
   0.1/ (0.1)
uscan info: newest_dir => '..'
uscan info: Requesting URL:
   https://download.gnome.org/sources/libmanette/../
uscan info: Matching pattern:
   (?:(?:https://download.gnome.org)?\/sources\/libmanette\/\.\.\/)?libmanette(?:[-_]?(\d[\-+\.:\~\da-zA-Z]*))\.tar\.xz
uscan warn: In debian/watch no matching files for watch line
  https://download.gnome.org/sources/libmanette/([0-9.]+)/libmanette(?:[-_]?(\d[\-+\.:\~\da-zA-Z]*))\.tar\.xz
uscan info: Scan finished