Instead of Patreon, you could link to a Ko-fi or Buy Me a Coffee page to accept tips or donations. However, you should make it abundantly clear that any tips or donations are not linked to being able to access the fanfiction. Instead, being a way to help support you as a writer.
Unless you plan to rewrite the story to be a completely original one, the chapters should remain available(free) to everyone rather than being placed behind a paywall or offered as donation/tip exclusive content.
If you like to use Patreon, I would recommend using it for original content. As it is a membership which might be seen as a means of paying for content.
Please do your own research though.
The story has truly been lovely to read so far. I resonate with the personality of Felix on a, weirdly, spiritual level.
