Investigate disabled rules after ESLint 9 migration

Some lint violations were disabled after the migration. In those cases I added a comment "Either fix this lint violation or explain why it's necessary to ignore.". We should follow up on these and investigate further if we can fix these somehow.

Start by locating the lint-violation comments added during the ESLint 9 migration and review the disabled rules around them. For each case, determine whether the violation can be fixed; done means the violation is fixed or the reason for keeping it disabled is documented.

Written by the indexing model from the issue text.