apt policy chromium
Installation candidate: 87.0.4280.88~linuxmint1+debbie
*** 87.0.4280.88~linuxmint1+debbie 100
500 http://deb.debian.org/debian buster/main amd64 Packages
500 http://security.debian.org/debian-security buster/updates/main amd64 Packages
That is what I have here, a direct install with dpkg under Debian Buster.
There is the repo of Mint for LMDE but it would pull too much packages that are newer than in Debian proper. I guess there would not be a real problem but in the future you might have them if you try to upgrade to the next release of Debian.
You can go with snap or flatpak but with all their problems. The theming is off (if you are not using Gnome) and Chromium starts awfully slow, especially the snap package. But they work.