That sounds like your install is bad. Amy's gameplay is supposed to look like this:
Maybe one of the asset downloads failed, so I'd recommend reinstalling it.
Okay, this was actually my bad. I had a mod installed,
Proper Super Forms, that added some abilities to Tails, Amy, Fang, and Metal. The flags it defines to give Amy a super form also re-enable the flags that prevent her from spin jumping. If I switch it out with
a different mod that only says "every character is allowed to go Super", Amy now spin jumps and can use her hammer with a shield. She can't do shield abilities, though; is
that intended? I think it's a
totally fair trade if so; her moveset is already
extremely capable and really fun!
Also, SRB2 vanilla has historically had multiple issues with its flatpak such as wayland support being completely busted (rphys forces x11) and no MIDI support which may cause no audio in srb2 the past. I agree SteamOS users should install the flatpak version, though I have no experience with immutable distros.
Is Wayland support being busted specific to the Flathub version, or is that something
any version of SRB2 suffers from? If it's the former, the way SRB2's Flatpak is built
could be part of it. I poked around and saw the stuff some (GNOME) folks were struggling with in your app submission. I think the SDL2 in FDO 23.08 has libdecor support, so some of what they were struggling with maybe could have been mitigated by including libdecor in the manifest...
...but why do that when Xwayland works fine? I mean, Gamescope kinda has the right idea; it is a Wayland compositor but does not support Wayland clients, only X11 clients through Xwayland. And SSD being broken is
literally only a GNOME problem and their own damn fault? Like... literally all of the Flathub maintainers are GNOME folks who are happy to force apps and downstreams to deal with their own stubbornness in refusing to implement SSD in Wayland. I'm certain there's not a single Plasma user among the Flathub maintainers. I would have loved for a Plasma Wayland user to have shown up like "Huh, that's weird. I have a titlebar running this in
my Wayland session, I wonder why you guys don't?

"
Anyways, never mind my sour grapes about all that, thank you for your help and the excellent mod!