CPU side channel mitigations on Pi 4 running Ubuntu 20.04?

I want to run a jumphost on Ubuntu 20.04 64 bit and Pi 4, as secure as possible. If I check lscpu of the vanilla install after running a dist-upgrade, I see this:

Architecture:                    aarch64
CPU op-mode(s):                  32-bit, 64-bit
Byte Order:                      Little Endian
CPU(s):                          4
On-line CPU(s) list:             0-3
Thread(s) per core:              1
Core(s) per socket:              4
Socket(s):                       1
Vendor ID:                       ARM
Model:                           3
Model name:                      Cortex-A72
Stepping:                        r0p3
CPU max MHz:                     1500.0000
CPU min MHz:                     600.0000
BogoMIPS:                        108.00
Vulnerability Itlb multihit:     Not affected
Vulnerability L1tf:              Not affected
Vulnerability Mds:               Not affected
Vulnerability Meltdown:          Not affected
Vulnerability Spec store bypass: Vulnerable
Vulnerability Spectre v1:        Mitigation; __user pointer sanitization
Vulnerability Spectre v2:        Vulnerable
Vulnerability Srbds:             Not affected
Vulnerability Tsx async abort:   Not affected
Flags:                           fp asimd evtstrm crc32 cpuid

So issues with Spectre v2 and Spec store bypass. Tried to fix it by adding the following to /boot/firmware/cmdline.txt:

spec_store_bypass_disable=on spectre_v2=on

But no luck / change 🙁

Any clues about how to fix this? Thanks!