How to use Flash in browser in 2021

# Step 1
Use a browser that still supports Flash (Basilisk, Pale Moon, Firefox-ESR(only for a limited time))

# Step 2
Edit mms.cfg so that flash doesn't auto-update or show EOL notice.
To do this go to:

32-bit Windows: %WINDIR%\System32\Macromed\Flash
64-bit Windows: %WINDIR%\SysWow64\Macromed\Flash
MacOS: /Library/Application Support/Macromedia
Linux: /etc/adobe/

Edit the file "mms.cfg" or create it if it doesn't exist (use Notepad++ on Windows).
The content of the file should be:

SilentAutoUpdateEnable=0 # disable automatic updates
AutoUpdateDisable=1 # disable update checking
EOLUninstallDisable = 1 # disable EOL notice
EnableInsecureAllowListLocalPathMatching = 1 # fixes bug with filenames with brackets, may also fix MPC-HC
AllowListUrlPattern = file:* # Allow all local files to run in browsers.

# Step 3 (Option 1)
Patch the latest version.
To do this go to the same directory as step 2, then depending on the flash version you have you need to edit a certain file.
Flash32_32_0_0_###.ocx (ActiveX: IE / IrfanView version)
Flash64_32_0_0_###.ocx (ActiveX: IE / IrfanView version)
NPSWF32_32_0_0_###.dll (NPAPI: Firefox / Palemoon / Basilisk version)
pepflashplayer32_32_0_0_###.dll (PPAPI: Chrome/Chromium/360/Edge version)

Copy it to desktop, remove read-only attribute, and edit this line with a hex editor like HxD, save, then replace the original file.
The strings to replace is
00 00 40 46 3E 6F 77 42
You need to replace it with
00 00 00 00 00 00 F8 7F

# Step 3 (Option 2):
In alternative instead of patching the latest version you can install an older version without killswitch (note: if you have the latest version installed downgrading requires extra steps).
https://archive.org/download/flashplayerarchive/pub/flashplayer/installers/archive/fp_32.0.0.371_archive.zip