Steps to reproduce
1 main menu, Preferences, LXQt Settings, Appearance
2 select Cursor
3 select Breeze Light
4 change Size from 34 to 40
5 click Apply
6 click on Close
6 restart the computer
On another box I have Devuan+LXQt and SLiM instead of SDDM,
This box doesn’t have the problem, cursor changes are fine.
So perhaps (?) the LXQt guys are also using a non-SDDM based setup.
(The other difference I noticed was that Devuan is also systemd-free, but I doubt systemd has anything to do with X startup).
So my personal theory is,
SDDM uses xrdb to load up X resources using ~/.Xresources.
But SLiM doesn’t do this (it makes no xrdb calls). And because of this, (somehow) SLiM triggers :LXQt to load the size from ~/.Xdefaults
(note: not ~/.icons/default/index.theme),
…which has the correct Xcursor.size.
In a fresh copy of Lubuntu (22.04-23.04), ~/.Xresources does not exist, so SDDM ignores it.
It also ignores ~/.Xdefaults (because it’s the old way of doing things).
But it still runs xrdb for other merges. And here is (another)
mystery - the cursor size ends up with some obscure small value e.g 21.
@ralf3u: still awake?
in absent of a solution, I present 3 quick workarounds;
Install and use a fixed size cursor,
e.g chameleon-cursor-theme
Chameleon-White-Large
or quicker;
Create an environment variable to fix the size;
Preferences > LXQT Settings > Session Settings > Environment >
Add > double-click fields
XCURSOR_SIZE 48
or even better;
Copy ~/.Xdefaults to ~/.Xresources after the change.
This will force SDDM to update the RESOURCE_MANAGER X property with the size found in ~/.Xresources.