Fan manga and other doujin works usually depends on the original copyright holder for enforcement.

Some are pretty open for any fanworks being commercialized as long it’s limited and case by case basis. For example, Love Live franchise allows doujin manga and other doujinshi works, but not with fanmerch. Serial Experiments Lain generally allows various stuff, but not R18 content. Some others like Yakitate Japan mangaka just happy seing his works have so many adult doujin manga, and even lining up on Comiket buying them.

Well, fuck. Most of people use F-Droid on “certified vendors” device.

Software and games.

No matter some people claims, there are always software/games that simply won’t run on Linux or no alternative available.

1. Non-Westerner that never have or realized alternative platform exist.
2. Artist that dependant on mainstream social media reach. (some artists already have 100K+ followers there, fedi also have limited reach due to instance blocking, e.g. you’re on Mastodon.art and want to reach Japanese audience (mainly misskey.io, but t was defederated on most of Western instance.)
3. People with social network bubble outside Westernsphere, they only have exclusively local feed on their Twitter.
4. People outside Westernsphere that already tried fediverse, but moving back as fediverse is still Western-centric or does not have their own community on feidverse.
5. Community that does not have monetary power to invest on their own fedi instance.