Is macOS Big Sur 11.7.10 still receiving security and maintenance updates?

Yes Big Sur is continuing to receive XProtect updates, as are OS X versions much older than it, but that fact and slow performance do not correlate.

If your Mac is performing poorly a fundamental first step is to determine if the same problems occur in "Safe Mode": Start up your Mac in safe mode - Apple Support. Use it for a little while in that mode, enough to characterize its performance. Then, reboot normally, and compare.

120 GB is an exiguous amount of storage these days but as small as it is it may not be a factor.

Short answer, no. Longer answer - it is theoretically possible that a security patch backward compatible to Big Sur could be pushed. But in practice that is extremely unlikely. XProtect updates will likely still be received (that can happen as far back as Mac OS X versions) and those aren't registered as "software updates" as they are background updates of the that XProtect does itself out of band.

Foxhole_531 wrote:

Hi, wondering if Big Sur is still getting software updates for security and maintenance? I assume it is, because my Software Update window says everything is up to date.

If Software Update tells you that everything is up to date, that means that your Mac is running the latest version of macOS with which it is compatible. It does not mean that your Mac is still getting software updates. It might be; it might not be. Software Update doesn't read the tea leaves as to whether Apple might issue future updates for old versions of macOS; it simply checks to see what is available at the time you run it.

Your Mac presumably is compatible with Big Sur – but not with Monterey, Ventura, Sonoma, or Sequoia.