On Friday 2022-12-02 on a desktop PC with MS Windows 11 Pro, and runing the Arduino IDE v1.8.19, a sketch
for a M5Stack Core2 would not compile while this sketch built successfully on 2022-04-24.

To investigate the problem, I turned on 'File > Preferences > Show detailed messages during compilation'.

I discovered that the name of the folder of the M5Stack board package contained a '+' character (ASCII decimal value 43, hexadecimal value 2B).
The compiler reported that it could not find (the) file(s). (see below).

There are some sources that describe the limitations of which characters can be used in the Microsoft Filesystems.
For example:
a) Naming Files, Paths and Namespaces;
b) Wikipedia Filename.

As far as I understand it: for the current Microsoft filesystem, NTFS, the '+' character is not a 'reserved character'.
That is probably why there is no error generated when installing the M5Stack board package with the '+' in the name,
however source b above mentions limitations in FAT12, FAT16 and FAT32 file systems. See the text in the most right column,
the text I marked with an orange rectangle. Here the '+' character is listed as 'reserved character'. In other words: one cannot
use the '+' character in file or folder names for these file systems:
.

Despite a successful install of the M5Stack board package, the compiler was not able to find files because of
the '+' character in the folder name.

Fortunately I was able to install the package with version ID: '2.0.5-1.0'. Next I was able to delete the package with version ID: '2.0.5+1.0'.
After this correction the sketch compiled and built successfully (again)

Here the last part of the build session with the compile error:

The offending folder location and name was:
C:\Users<User>\AppData\Local\Arduino15\packages\m5stack\hardware\esp32\2.0.5+1.0

Today, when using the newest version of the Arduino IDE (version 2.0.3), I was asked to update a boards package from M5Stack.
While the version 2.0.5-1.0 was installed, the Arduino IDE suggested me to install the M5Stack version 2.0.5+1.0. Again the version
with the '+' sign in the version (and sure, the folder name too). With my previous experience I did not install the proposed update. (See the partial screenshot below):

Maybe I address the wrong persons with this post.
Perhaps I should report this problem to the maintainer(s) of the compiler used in the Arduino IDE.

Can I ask the moderators of this M5Stack forum to look into the matter and take corrective measures, if you think that is necessary?
Thank you.