It appears that you (GeoLuz and tox1c90) are in the "exception" rather than "rule" category for Enpass v6. It also appears you are primarily Edge and smartphone users of Enpass, both of which are incredibly castrated environments compared to the full-function desktop experience we have with Enpass v5 in full-function browsers like Firefox, Safari, Chrome on a desktop.
As for compatibility issues, if version 5 ran reliably and flawlessly, then as soon as v6 installed by Enpass's auto update and completely blew up (extension can't reliably connect with the application, can't find the data store, and when it does hook up, can't auto-invoke the credentials for the log-in page you have invoked - the most basic reliable function of version 5) then the onus is on Sinew Software, NOT users, to fix the problems. The sheer volume of problems indicate this was an update to please Enpass, and the fancy Windows messaging version (so Microsoft can insert itself into your machine security situation and try to force you into OneDrive client-hood). There was apparently no or little attention paid to impacts of design and coding changes to the "Traditional" version and interfaces with non-Microsoft extensions.
The fact that Sinew Software remains silent, provides no updates to address all these issues and no help to those they apparently ignored in the beta test / release cycle indicates that their roadmap is a Microsoft / Edge / Window phone / OneDrive centered plan so that users of non-Microsoft browsers can just fall to the wayside, live with the problems or find other products that actually work with non-Microsoft browsers and cloud services. The Sinew Software silence, their lack of effort to address these issues is the coward's way out - they should just tell Firefox, non-MS cloud service users etc. that they will no longer support these browsers / services and make a clean break with those users who have been forced back to version 5 with all the SERIOUS functionality and reliability downgrades the auto-update to version 6 inflicted upon them.
But I'm happy that those who are enamored of Edge and OneDrive, Microsoft Store app versions etc. have a product that works for them. It is still no help for the rest of us who swallowed the Sinew Software "good will" based on experience through version 5 on other browsers.