You can enable or disable SSL/TLS ciphers according to your own security preferences. Go to about:config and filter for security.ssl3 and you'll see all available cipher suites for SSL 3.0 through TLS 1.2. Filter for security.tls13 to see the available cipher suites for TLS 1.3. Set to true to enable or false to disable. Changes are stored in your profile so they'll "stick" between browser updates; but you have to do this for every browser profile you use.
A few Web sites may not yet use newer, more secure ciphers; if you visit any of those, you'll need to leave a less secure cipher enabled to access it. If you disable some ciphers, then can't connect to a site, that's probably the reason. Create a new, "clean" profile, restart the browser specifying it, and try again. If it works, check which cipher your browser uses with a particular site by clicking the padlock, then the right arrow, then "More Information." Then restart your browser with the default profile, and re-enable the cipher your browser used with that site. Your communications with that site are probably still reasonably secure, but be aware that they could eventually be decrypted by someone determined enough; perhaps even years later, and act accordingly. Ideally, you should contact the Webmaster and ask them to enable newer, more secure ciphers. (The Web site may choose to leave some older ciphers enabled as well, for compatibility with older browsers. That's fine as long as the newer ones are preferred.)