Same here aas in comment #15.  I didn't have SSSD installed prior to the upgrade and it was "ubuntu-desktop-minimal" that pulled SSSD in.  Not only did it break my automount but also login and sudo would take about a 4 seconds delay to succeed - as I guess it was trying to auth via SSS.

Grepped from the update log:
apt.log:  Installing sssd as Recommends of ubuntu-desktop-minimal
apt.log:    MarkInstall sssd:amd64 < none -> 2.3.1-2 @un uN Ib > FU=0
apt.log:    Installing python3-sss as Depends of sssd
apt.log:      MarkInstall python3-sss:amd64 < none -> 2.3.1-2 @un uN > FU=0
apt.log:    Installing sssd-ad as Depends of sssd
apt.log:      MarkInstall sssd-ad:amd64 < none -> 2.3.1-2 @un uN Ib > FU=0
apt.log:      Installing libsss-idmap0 as Depends of sssd-ad
apt.log:        MarkInstall libsss-idmap0:amd64 < none -> 2.3.1-2 @un uN > FU=0
apt.log:      Installing sssd-ad-common as Depends of sssd-ad
apt.log:        MarkInstall sssd-ad-common:amd64 < none -> 2.3.1-2 @un uN Ib > FU=0
apt.log:        Installing sssd-common as Depends of sssd-ad-common
apt.log:          MarkInstall sssd-common:amd64 < none -> 2.3.1-2 @un uN Ib > FU=0
apt.log:          Installing libc-ares2 as Depends of sssd-common
apt.log:          Installing libdhash1 as Depends of sssd-common
apt.log:          Installing libini-config5 as Depends of sssd-common
apt.log:          Installing libsss-certmap0 as Depends of sssd-common
apt.log:            MarkInstall libsss-certmap0:amd64 < none -> 2.3.1-2 @un uN > FU=0
apt.log:          Installing libsss-nss-idmap0 as Depends of sssd-common
apt.log:            MarkInstall libsss-nss-idmap0:amd64 < none -> 2.3.1-2 @un uN > FU=0
apt.log:          Installing libnss-sss as Recommends of sssd-common
apt.log:            MarkInstall libnss-sss:amd64 < none -> 2.3.1-2 @un uN > FU=0
apt.log:          Installing libpam-sss as Recommends of sssd-common
apt.log:            MarkInstall libpam-sss:amd64 < none -> 2.3.1-2 @un uN Ib > FU=0
apt.log:            Installing libpam-pwquality as Depends of libpam-sss
apt.log:          Installing libsss-sudo as Recommends of sssd-common
apt.log:            MarkInstall libsss-sudo:amd64 < none -> 2.3.1-2 @un uN > FU=0
apt.log:      Installing sssd-krb5-common as Depends of sssd-ad
apt.log:        MarkInstall sssd-krb5-common:amd64 < none -> 2.3.1-2 @un uN > FU=0
apt.log:    Installing sssd-ipa as Depends of sssd
apt.log:      MarkInstall sssd-ipa:amd64 < none -> 2.3.1-2 @un uN Ib > FU=0
apt.log:      Installing libipa-hbac0 as Depends of sssd-ipa
apt.log:    Installing sssd-krb5 as Depends of sssd
apt.log:      MarkInstall sssd-krb5:amd64 < none -> 2.3.1-2 @un uN > FU=0
apt.log:    Installing sssd-ldap as Depends of sssd
apt.log:      MarkInstall sssd-ldap:amd64 < none -> 2.3.1-2 @un uN IPb > FU=0
apt.log:      Installing ldap-utils as Recommends of sssd-ldap
apt.log:    Installing sssd-proxy as Depends of sssd
apt.log:      MarkInstall sssd-proxy:amd64 < none -> 2.3.1-2 @un uN > FU=0
apt.log:  new important dependency: sssd-tools:amd64
apt.log:  Installing sssd-tools as Recommends of ubuntu-desktop-minimal
apt.log:    MarkInstall sssd-tools:amd64 < none -> 2.3.1-2 @un uN IPb > FU=0
apt.log:    Installing sssd-dbus as Recommends of sssd-tools
apt.log:      MarkInstall sssd-dbus:amd64 < none -> 2.3.1-2 @un uN > FU=0
apt.log:  new important dependency: sssd:amd64
apt.log:  Installing sssd as Recommends of ubuntu-desktop-minimal