Firefox-51.0.1 [32-bit] with Adobe Flash Plugin 24.0.0.221 the current versions work on my 5.0 full install.
Use this command as root while connected to the internet:
tazpkg -gi flash-plugin --extra
Restart firefox, test install here: http://www.adobe.com/software/flash/about/
root@slitaz:/home/tux # tazpkg -gi flash-plugin --extra
Folder "/var/cache/tazpkg/extra/packages" does not contain packages
Connecting to fpdownload.adobe.com (104.91.172.77:443)
flash_player_npapi_l 100% |*******************************| 8947k 0:00:00 ETA
Find depends...
for libplds4.so
Packing package "flash-plugin-24.0.0.221"
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Creating the list of files... [ Done ]
Creating md5sum of files... [ Done ]
Compressing the FS... [ Done ]
Updating receipt sizes... [ Done ]
Creating full cpio archive... [ Done ]
Restoring original package tree... [ Done ]
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Package "flash-plugin-24.0.0.221" compressed successfully.
Size: 6.1M
Tracking dependencies for package "flash-plugin"
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Missing package "webian-shell"
Missing package "ossp-uuid"
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2 missing packages to install.
Unable to find package "webian-shell" in the extra packages list.
Unable to find package "ossp-uuid" in the extra packages list.
Installation of package "flash-plugin"
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Adobe Flash Player.
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Copying package... [ Done ]
Extracting package... [ Done ]
Remember modified packages... [ Done ]
Installing package... [ Done ]
Removing all tmp files... [ Done ]
Execute post-install commands... [ Done ]
Processing post install commands... [ Done ]
Update system databases... [ Done ]
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Package "flash-plugin" (24.0.0.221) is installed.