With the upcoming Kernel Feature Freeze (September 16th) and Kernel Freeze (September 30th) development stages, it would appear that Ubuntu 21.10 (Impish Indri) is sticking with Linux kernel 5.13, which recently landed in the main archives of the distribution as the default kernel instead of the Linux 5.11 kernel used until now from the Ubuntu 21.04 (Hirsute Hippo) release.
Linux kernel 5.13 has been released at the end of June 2021, and it introduces initial support for Apple’s M1 processor, support for the Landlock security module to create safe security sandboxes for mitigating the security impact of various flaws in user space apps, as well as the ability to handle ASN.1 trusted keys.