[floatboth]

Not always line 21. Some stuff can appear before CPU info — like hypervisor info and some weird errors:

    …
    SRAT: Ignoring memory at addr 0x80000200000
    VT(efifb): resolution 1024x768
    Hyper-V Version: 10.0.15063 [SP0]
      Features=0x2e7f<VPRUNTIME,TMREFCNT,SYNIC,SYNTM,APIC,HYPERCALL,VPINDEX,REFTSC,IDLE,TMFREQ>
      PM Features=0x0 [C2]
      Features3=0xed7b2<DEBUG,XMMHC,IDLE,NUMA,TMFREQ,SYNCMC,CRASH,NPIEP>
    Timecounter "Hyper-V" frequency 10000000 Hz quality 2000
    CPU: AMD Ryzen 7 1700 Eight-Core Processor           (3000.00-MHz K8-class CPU)
    Origin="AuthenticAMD"  Id=0x800f11  Family=0x17  Model=0x1  Stepping=1
    …

but it's always in the first part of dmesg.