uBlock Origin's syntax support is second-to-none compared to just about any other web extension known to man, including uBO/AdGuard/ABP lists, domains lists, hosts files, and in certain cases IP lists. That being said, my extensive work on FilterLists.com in the past 12 months have taught me about many unusual list syntaxes that to the best of my knowledge are not currently supported by uBO, so I'm hereby suggesting that such support could be made. Most of the syntaxes are rarely applied outside of enthusiast or business circles, but indeed they are in use by some people out there.

My suggestions along with the easiest possible conversion approaches:

• hosts.deny files (Example list): Make ALL: example.com equivalent to example.com
• Unbound lists (Example list): Make local-zone: "example.com" redirect equivalent to example.com, while discarding local-data: "example.com A 127.0.0.1"
• dnsmasq lists (Example list): Make address=/example.com/127.0.0.1 equivalent to 127.0.0.1 example.com or to example.com
• BIND lists (Example list): Make zone "example.com" { type master; notify no; file "null.zone.file"; }; equivalent to example.com
• RPZ lists (Example list): Make example.com CNAME . equivalent to example.com
• Internet Explorer Tracking Protection List lists (Inoptimally made example list):

If I understand https://docs.microsoft.com/en-us/previous-versions/windows/internet-explorer/ie-developer/platform-apis/hh273399(v=vs.85) correctly, then the following conversions may potentially be used:

• -d example.com → ||example.com
• -d example.com file → ||example.com/file^ or ||example.com/*/file^
• - file → */file/
• +d example.com → @@||example.com
• : expires = → # Expires:

I've however chosen to not suggest compatibility conversion for Privoxy lists (Example list), because .example.com may have legitimate unique uses in uBO as-is; whereas Little Snitch lists have too many parameters to easily ensure successful conversions, with each of the 5 such lists on FilterLists.com using different entry structures.

You are welcome to add support for whichever ones of these that you want to; I am in no way trying or intending to pressure you to add all of them.