I'm sorry if I'm out of line with my comment here, but this whole post gave me a good laugh. I think it's akin to asking GIMP developers, "why don't you just make this like Photoshop" or asking Linux developers, "why don't you just make this like Windows".
I'm sure the Thunder devs would love to bring over a lot of the most popular features from Sync, but it's not that simple. Looking at the repo, there are already very frequent commits and releases, but there is also quite a backlog of feature and bug requests. You can't just make one app like another app, nor can you imply that Thunder doesn't have feature parity with Sync because the devs don't want it to.
Add on to that the fact that Sync is a paid app meaning that the developer can justify spending more time on it than an open-source app maintained in the spare time of the devs.
Anyway, that's just my two cents. In short, "it's not that simple". :-)
Keep in mind that VPSs will charge for bandwidth, which adds up quickly when you're streaming.
One suggestion I haven't seen mentioned is contacting your ISP. Sometimes you can get a dedicated IP, although you might have to pay for it.
Alternatively you might just break down and pay for Plex Pass. I know that goes against the Lemmy philosophy to the very core, but for all its issues, Plex is still way ahead of Jellyfin in terms of features, UI/UX, etc. Jellyfin will get there, and I'm ready to switch the day that Plex becomes unusable, but that hasn't happened yet.