- MediaWiki 1.35.0-rc.2 (37ef236)
Explicit loading is not required for extension Parsoid according to @matmarex at T261044#6406311.
But Parsoid is not listed as an installed extension in Special:Version and VE(If installed) seems to be broken by default;
After appending wfLoadExtension( 'Parsoid', "$IP/vendor/wikimedia/parsoid/extension.json" );, I could see Parsoid listed.
I launched MediaWiki by the way described in DEVELOPERS.md with SQLite and with my own Docker compose file with MySQL, so T259685 is not about this.