This is an AUFS equipped real time configured kernel built in Fossapup64 which will work also in Bionic64.
The download name of the huge kernel file contains "fossapup64" but is 5.13.1-rt1.
▶—— Linux Kernel ——◀
Kernel Release: 5.13.1-rt1
Build Date: Wed Aug 18 20:59:00 EDT 2021
Build GCC: 9.3.0-10ubuntu2)
OS Support: GNU/Linux
Architecture: x86_64
SMP Enabled: Yes
Direct download -> https://rockedge.org/kernels/data/kerne ... 64.tar.bz2