All these distros are very similar. You just use dnf instead of apt, thats its. And repos get synced automatically.
If you really really want to stay on the apt side (I wouldnt), you can use the OG Lubuntu, which was a driving force in LXDE and LXQt development. But you will want to run unsnap to remove the bloat and make it as small as possible.
LXQt uses less RAM than XFCE and it is now fully based on Qt6. XFCE is based on XOrg which is not maintained since forever. LXQt is really close to being Wayland ready, which is also faster and more efficient than XOrg’s spaghetti code.
But as Ubuntu progresses too slow to get the latest cool stuff, I would recommend Fedora. It really is nice.