Depends on your risk model. To simplify my point of view: risk = severity * likelyhood. If it's unlikely and relatively nonconsequential to overcome, it's still low risk.

There is a world where running an old kernel and latest firefox gets you hacked, say maybe buggy GPU drivers with a really really bad opengl vulnerability?. I think it's quite unlikely. Like what hacker targets your weird GPU driver several years out of date?

I think it's much more likely your few-days-outdated LTS version of firefox gets hacked instead, because even if you have an old and fully supported distro, updates are often a bit more delayed (backporting patches takes still some time from maintainers). LTS distro maintainers also do choose what bugs and vulnerability get backported or not, and not everything crosses the line.

If you do things like accessing your bank with your life savings or your crypto wallet then please do get a more modern distro and live with the hardware incompatibilities. If you use it to browse facebook and the news, read emails and write some random documents, there's not much there to steal for a hacker anyway.

IMHO just the fact you are not running windows and are on the latest version of the software means you'll be all fine, for many, many years, even with an old, unsupported kernel. Your old pc will probably die before a hacker gets in.

If you have compliance requirements from your company... get your company to buy you a better, more modern pc please. Like, wtf, that thing has probably hardware and firmware vulnerabilities too!