KeePassXC Password Manager
...a free and open-source password manager. It started as a community fork of KeePassX [archive] (itself a cross-platform fork of KeePass [archive]). ... The Electronic Frontier Foundation [archive] mention KeePassXC as "an example of a password manager that is open-source and free." The tech collective PrivacyTools has included KeePassXC in their list of recommended password manager software because of its active development.
KeePassXC is recommended by the EFF in their Surveillance Self-Defense [archive] guide  and it is considered a feature-rich, modern and fully cross-platform password manager; refer to the features list [archive] and FAQ [archive] for more detail. The benefits of a password manager include: 
- Strong and unique passwords can be created and stored by the one application.
- Responses to security questions can be safely stored. 
- All passwords can be protected by a single master password/passphrase.
- This methodology prevents the reuse of passwords across multiple services, which is a poor security practice.
- This provides better account protection, particularly when combined with Two-factor Authentication (2FA).
Note that KeePassXC does not automatically save changes when it is used, so this should be changed in the settings (otherwise unsaved password changes could be lost).
Reliable, open-source password managers are a useful tool but they also come with risks:
- Password managers create a single point of failure.
- Research suggests coding vulnerabilities are present in many password managers.
- Highly capable adversaries are likely to target password managers.
- Avoid storing passwords "in the cloud" (on remote servers) -- this is more convenient but introduces the risk of a cloud vulnerability leading to an exploit.
- Avoid crossing remote borders with electronic devices containing your password manager -- some jurisdictions can compel/demand password disclosure and the unlocking of devices. 
Before using a password manager like KeePassXC, conduct a risk assessment of your personal circumstances. If you are likely to be targeted, then consider creating strong passwords manually instead and storing them in a safe physical location. One suitable method is EFF's Dice-Generated Passphrases [archive] via their long wordlist [archive]. Note that passphrases should be at least six words long; passphrases of 15 words or more will protect against future quantum computer advancements. 
KeePassXC Setup and Use
Troubleshooting: Time Fix
Whonix ™ Offline Workstation
Since Whonix ™ uses Secure Distributed Web Date (
sdwdate), there will be a delay in the TOTP 30-second period. For example, if
sdwdate has enforced a 22 second delay, then a TOTP code copied and pasted into a website or service that requires it would not work until the timer reached eight seconds or below. (This result was tested in an offline
whonix-ws standaloneVM in Qubes OS.)
To avoid delays, disable
bootclockrandomization by running this command:
sudo service sdwdate stop && sudo service bootclockrandomization stop
KeePassXC Browser Extension
|Community Support Only!:|
It is possible to install the official KeePassXC browser plug-in for FireFox/Tor Browser. If utilized, this allows KeePassXC to store passwords and auto-type them into various websites and applications. This configuration is unrecommended because any software vulnerabilities might unintentionally expose sensitive passwords.
- https://en.wikipedia.org/wiki/KeePassXC [archive]
- It is also recommended by PrivacyTools [archive], see here [archive] (v3 onion [archive]).
- https://ssd.eff.org/en/module/creating-strong-passwords [archive]
- It is recommended to provide fictional information to security questions in order to limit personal disclosures. Honest answers might be discoverable by adversaries who then utilize it to bypass your passwords completely.
- The US border is a case in point, see: Digital Privacy at the U.S. Border: Protecting the Data On Your Devices [archive].
- Quantum computers halve the number of iterations required to brute-force a key. This means doubling the length of symmetric keys to protect against future (hypothetical) quantum attacks.
- This is because accurate time is a precondition for TOTP -- Whonix ™ randomizes this value due to Boot Clock Randomization and sdwdate.