Xubuntu 26.04, with the XFCE Desktop Environment, still uses X11. So if you want to run Ardour in native X11 and aren’t vehemently opposed to switching your DE, that’s an alternative to sticking to 24.04.
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Thank you @peder for the comment, it’s helpful to fill out my picture of 26.04 overall. My understanding is that while Ubuntu Studio 26.04 LTS will use KDE + Wayland by default, it will be possible to manually install X11 and use it natively. I won’t upgrade until I’m convinced that’s true.
As far as XFCE is concerned, I used it daily as a contract engineer designing chips for a big company, and it was fine. But at this point I’m kind of married to KDE (see user name).
Thanks again, appreciate it.
Probably not related to your issue at all, but Ubuntu LTS does tend to stay with older packages, including QT as well as many other things (pipewire comes to mind). While it does include Qt6 it uses an older version, v6.6. Qt is already at v6.11 but their policy does not allow for upgrading even for POINT releases apparently and this has been an issue for one of my projects. There was a change between Qt6.6 and Qt6.7 which breaks a lot of stuff and the Ubuntu/Kubuntu project refuses to address it. I can understand not upgrading Qt6 to Qt7 on a LTS release, but for a point release, this is beyond ridiculous.
Fortunately for my project (FreeFactoryQT), I was able to create a compat script to make it work with Qt6.6 but it took me two weeks to figure it out.
A hint for the developers: If you tell Ardour on startup not to display the memory limit warning again it no longer crashes on next startups. The problem is that Ardour displays the warning while the GUI is not yet fully loaded and then waits for the OK to continue loading the GUI. Maybe one can decouple both tasks.
Configuration: Kubuntu 26.04 LTS with Wayland
Hint for users: 
Why not configure your system for pro audio, so the warning is never displayed instead?
Besides it is a bug in wayland that needs fixing, there are also modal dialog windows with similar issues.
I tried it but somehow failed, and since I do only edit work I did not invest more time for a possible fix.
I realized this later. Opening a dialog of any plugin leads to a crash.
For the time being (as temporary workaround) I use an older notebook with Xubuntu 24.04 which uses X11 instead of Wayland.