On my laptop's Core i5-10210U with mitigations=off, the demo just prints "[!] error: could not infer memory layout" until it runs out of retries.

This is on Chromium 91.0.4472.106 and kernel 5.12.11-arch1-1. lscpu shows vulnerabilities:

    Itlb multihit:         KVM: Mitigation: VMX disabled
    L1tf:                  Not affected
    Mds:                   Not affected
    Meltdown:              Not affected
    Spec store bypass:     Vulnerable
    Spectre v1:            Vulnerable: __user pointer sanitization and usercopy barriers only; no swapgs barriers
    Spectre v2:            Vulnerable, IBPB: disabled, STIBP: disabled
    Srbds:                 Mitigation; TSX disabled
    Tsx async abort:       Not affected

I got the same result on a pretty similar system.

The problem is that PoC is extracting data which the PoC itself created specifically to facilitate said extraction. AFAIK no one has created a PoC which can extract specific data which hasn't been constructed to facilitate the PoC.