- Users of LMDE 2 Cinnamon can upgrade in place to LMDE 3.
- Users of LMDE 2 MATE will have to reinstall because of LMDE 3 no longer has a MATE release and there are incompatibilities for MATE packages between LMDE 2 and the new Debian Stretch package base for LMDE 3.
Relevant bits from the monthly news:
The upgrade path for the Cinnamon edition was also opened. Timeshift, Slick Greeter and mintupgrade were backported towards LMDE 2 to facilitate the upgrade and the switch from MDM with sysvinit to LightDM with Systemd.
If you are running LMDE 2 Cinnamon, please upgrade before the end of the year. We’ll continue to support LMDE 2 until the 1st of January 2019.
The LMDE 2 MATE edition cannot be upgraded (Debian’s version of MATE is only 1.16 and this edition is no longer present in LMDE 3), we recommend users perform data and software backups and upgrade their OS via fresh installations. MATE packages in LMDE 2 will also be supported until the 1st of the January 2019.