Lubuntu 20.10 to 21.10 ?
You mention an upgrade from 20.10 to 21.10; an unsupported upgrade path, and didn’t say how it was achieved, thus I wonder if you did something you shouldn’t have and have created issues yourself (20.10 release-upgraded to 21.04; from 21.04 you release-upgraded to 21.10; not direct)
Swap enabled? Is it large enough?
Do you have swap enabled? and if it’s enabled; is it large enough? Lubuntu 21.10 defaults to having swap enabled, but it’s rather small & doesn’t fit all uses of the OS; I for one would increase the size on my old 2009 hardware.
Kernel Modules (drivers)
Additional drivers are done the same way in both Lubuntu 20.10 though 21.10; in the manual it’s found in https://manual.lubuntu.me/stable/4/4.3/software_sources.html (see “Proprietary Drivers”), at least from a user standpoint.
From a technical one, drivers are actually kernel modules which means they’ll have changed as 20.10 used the 5.8 kernel, 21.04 the 5.11 kernel & 21.10 uses the 5.13 meaning you’ll be using the appropriate kernel module (driver) for that kernel thus change. Lubuntu LTS releases offer two kernel stacks; so for older hardware you can use the GA stack that doesn’t change which can often perform better than newer kernels (newer hardware tends to need later kernels) but that’s not an option available for non-LTS release.