I would humbly suggest that Ubuntu is releasing kernel bugs fixed long ago by Debian. The future of Ubuntu is uncertain with its owner looking for an IPO:
https://www.zdnet.com/article/canonical ... -ipo-path/Canonical will devote more of its time to "putting the company on the path to a IPO. We must figure out what steps we need to take moving forward." That means focusing on Canonical's most profitable lines.
Debian on the other hand is a community driven distribution focused on releasing a free, stable, operating system:
Debian has become much more user friendly over the past few years. Mint has obviously already thought it a good idea to have Debian as a back up with Linux Mint Debian (LMDE). I would suggest an emphasis on the LMDE release and gradual move toward a complete Debian base for Mint by the Mint 20 release.
Whether or not Ubuntu sells to another owner, I would suggest its motivation and focus is diverging from Mint, and has been doing so for quite awhile.
I am just a user and fan of Mint. Clem and his team have listened to their users more than just about any other Linux distribution. And I have seen them make wise moves all along, from going to an LTS base for main Mint, and Debian Stable for LMDE. Before that when Gnome 2 became an unrecognizable Gnome 3 and Ubuntu changed its DE, Mint did as well, but Mint stayed with the familiar traditional type of DE that has served them so well.
A Mint fully based upon Debian would allow its users the freedom to stick with a Stable release not subject to constant breakage from an upstream Ubuntu base. For users wanting more cutting edge options they could switch sources to either Debian Testing or Debian Sid at their own risk. Yet at this point even Debian Sid looks more reliable than an Ubuntu 18.04 base.
I wish Mint nothing but the best, that is why I am offering this suggestion.