I wouldn't touch that.
There's an EOL timestamp in recent versions of Flash Player. It can be altered so latest Flash Player continues to work as usual.
Find a hexadecimal string 000040463E6F7742 in NPSFWXX_32_0_0_465.dll (XX = bitness, either 32 or 64) with a hex editor, replace it with eg. 0000C02055148042, that will just change the year from 2021 to 2040. It's a unique string, so only one will be found as long as you got the right file. The string represents time elapsed since Unix epoch in milliseconds, stored as 64-bit double precision float number (no fractional part).
The DLLs are in:
C:\Windows\System32\Macromed\Flash - 64-bit Flash on 64-bit OS or 32-bit Flash on 32-bit OS
C:\Windows\SysWOW64\Macromed\Flash - 32-bit Flash on 64-bit OS
This is for NPAPI version, but should be doable with PPAPI and ActiveX versions as well, though I haven't tried those. Doing this obviously invalidates the digital signature on the DLL. Pale Moon (and probably other browsers) doesn't mind. I wonder if Flash app could check it.
Also, PE checksum is invalidated, but that can be fixed with certain tools. I think there's a high probability that altering Flash binaries doesn't cause any side effects beyond what modifications you did achieve.