I was confronted with similar problems in the course of a new installation on another computer in the last few days. What I can say with certainty is that the system as a whole is extremely vulnerable and completely insecure during the installation process! At this point, I would also like to expressly issue a warning to all users:
For the time being, refrain from any new installation as long as these problems have not been solved!
For me it was clear in the last four days how vulnerable and inconsistent the software in LMDE5 is overall. How can it be that an existing application suddenly stops working during an installation process? Why is the system telling you that a possible installation can only be continued if you remove certain libraries beforehand, without saying immediately which ones, and replace them with others manually, which, however, initially impairs the function of other applications? The time it takes just to find out exactly where the problem is is immense. The matter only becomes really painful when the affected program is none other than "Mintinstall" of all things.
It was only after a nerve wracking search in Synaptic that I was able to see exactly what was blocking the installation process and then step by step eliminate several problems. I had a total of 330 objects (packages, programs and other system components) to be installed. It soon became apparent that the order of the updates plays an important role here, but the system apparently has no control over which priorities are to be set in the order. The most important thing about the updates are the program extensions, only then should the security updates be processed gradually. Only after about 85% of all components were installed was the system, including Mintinstall, error-free and fully operational again.
I had never seen anything like this with Mint before, something that probably unsettles every user.