Here is a quote from seamonkey project:
About SeaMonkey "The SeaMonkey project is a community effort to develop the SeaMonkey all-in-one internet application suite. Such a software suite was previously made popular by Netscape and Mozilla, and the SeaMonkey project continues to develop and deliver high-quality updates as well as new features and improvements to this concept. Containing an Internet browser, email & newsgroup client, HTML editor, IRC chat and web development tools, SeaMonkey is sure to appeal to advanced users, web developers and corporate users. SeaMonkey is built on the open source Mozilla Gecko engine, the same code which underlies the highly successful Thunderbird and is the base for the Firefox browser. SeaMonkey benefits from the cross-fertilization with these other projects, by gaining (and contributing) new features and the ongoing security updates which are a modern necessity. The SeaMonkey Association provides legal backing for the SeaMonkey Project."
I really like Seamonkey. Lighter, more features like the editor, mail, irc, calendar and feed support. Where it struggles is poor sites only working with either Firefox and Google chrome. It's highly extendable via xpi addons. ublock origin, and the "little monkey" theme being the main ones I add. You might need to change the seamonkey version on little monkey.
you can either unpack and edit the xpi or use addon converter
to edit it for later versions of Seamonkey
Ublock origin the one addon you really need if you're using a modern browser with javascript turned on
Especially during covid I had to do my NHS appointments on line. I couldn't use seamonkey without this addom. It's a toolbar button for SeaMonkey to override the missing WebRTC permissions dialog and allow media capture automatically. Please read the site for info on this plugin as it must not be left on when not being used unless you want to give someone access to your webcam and mic!
Cookie exterminator. Lets you set up some rules for cookies. It can accept them and then delete them once you're in the site. You can also white list.