Open With - Files Associations - Changed Default Browser, The .html And .htm File Associations Had Been Set To "unknown"

Having changed my default browser, the .html and .htm file associations had been set to "unknown". Don't ask me why. Trying to set them via the usual mechanisms: "open with" or "file associations" menus does not work because they are populated only with MS programs. All attempts to select other programs via "browse" option fail. I can select the program but it is simply ignored and no change to the file associations happens. Nor is the selected program added to the list of programs available for selection. As there is no option provided for typing in the full path, as used to be the case with earlier and better operating systems, and the "browse" option does not work, I am totally stuck.

Is this a new MS policy to prevent users from running non-MS programs?? Whatever it is, it is very frustrating and affects all programs and extensions, not just the .html of the above example. Another very annoying thing is that even when I manage to run some non-MS programs manually, they will only work if run in "admin mode", as they are prevented from writing to disk. Are users not supposed to be allowed to write to our own disks anymore????