Firefox-Hilfeforum

I'm trying to upgrade from V52 ESR - kept for known and obvious reasons concerning addons compatibility - to a current V81. Copied the profile data from user/appdata/mozilla/firefox.../myprofile/*.* - including "key3.db" (in use), "key4.db" (don't know where this one originates from - shouldn't exist at all for versions < 57 or so) and "logins.json".

So far stumbled upon:

• No Logins in new system visible. No master password set. After setting a new master password, still no logins visible.
• This very forum here suggests - in many threads for version upgrades from somewhere in the 50s to up to the 70s - to simply copy the "key3.db" and "logins.json" and to delete the "key4.db" on the new system's profile. That does not change anything at all.

Am i forced to keep the V52, now not only by means of addons compatibility, but also by means of login manager compatibility?

What would the correct path to upgrade be? Would i have to install each and every in-between-version from 52 to 81 to be able to migrate? Will i run into the exact same trouble doing it that way, only burning daytime for nothing? Or is it guarantied to somehow get the logins data transfered to the current version? How did all the Millions of other users fare with that aspect? Is that an extremely rare case where users set a master password, so that developers decided to not care anymore about those nasty paranoids?