It is perfectly safe, so long as you are keeping all your other packages up to date, because your distro should allow you the ability to have more than one kernel installed at a time.
If you 're using the GRUB bootloader, just hold down shift at boot to see the menu and chose which one to use. It will default to the highest number, unless you have previously selected a different one. Then, if you have problems with 5.10, you can uninstall it and go back to 5.8.
Never only have one kernel installed. Always good to have a second (mostly the latest LTS kernel) available to fallback on.
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