I'd always suggest reading the release notes, and taking note of the announcements put out by teams, eg.
Ubuntu's Discourse (where the Ubuntu Summit 25.10 is being held currently) also highlights what is supported in the Support and Help section where you'll note (open the Before Asking detail) only questions about Ubuntu Mate 24.04 LTS, 25.04 & 25.10 are included. Ubuntu 22.04 LTS Desktop and Server questions are still on-topic, but not even Ubuntu-MATE 22.04 LTS is. If you'd have asked this question on the Ubuntu Discourse, I (or another moderator) would have likely quoted from that page & closed your question as off-topic; as 20.04 isn't supported (even using Ubuntu Desktop; Ubuntu Discourse is Ubuntu support, and not the Canonical discourse).
You mention browsing, which was one area where support is really limited except via snap packages in focal (20.04) so I do suggest you read the security notices for your chosen release. Most of the deb packages still receiving updates are for server platforms, not desktop (clients) in the browsing area.
This site has a more relaxed status where the MATE desktop is specified (even where 20.04 is EOL/EOSS), as this is ~both a MATE and Ubuntu-MATE site.
If security matters to you, read and learn about what you're using, and don't just trust AI (it's correct maybe 85% of the time [my current opinion], but do especially poorly in regards accuracy in 'timing', as AI uses older texts as its knowledge base)