Firefox
SeaMonkey
@number12345 whilst I can’t comment on compatibility with the five extensions that you mention, I do know that some of the gems that became legacy for Firefox remain good with SeaMonkey.
Some of the extensions that are not immediately compatible can be successfully fed through this service:
Extension Converter for SeaMonkey
I’ll find, or begin, a separate topic to list the converted extensions that are good for me.
– thanks – and I assume that if SeaMonkey progresses to support a subset of WebExtensions APIs, the progress will not preclude reasonable use of other types of extension.