A regular user can do select version() or select @@version it's the same version string.

serg,

A regular user can do select version() or select @@version it's the same version string.

It's not the same string. The --version output contains @@version, but in the format Mohammed Mateen suggested, the maturity is placed between progname and Ver literal, which means it would have to be added directly to the printf. The server_version string starts after Ver.

I understand that the above suggested format can potentially break scripts as identified by:
elenst,

it will probably break a countless number of custom scripts which parse the line.

hence reworked some more formats for this issue.
1) Displaying it when the client logs in:

2) Displaying the maturity as a variable as suggested by serg

3) We could also combine formats 1 and 2.

Hope this works.

Please help me start the implementation by selecting any of the suggested formats or do suggest what else could be done to fix this issue.

Let's put it in the version, after "MariaDB". Like in 10.5.2-MariaDB-gamma.

Note that for MariaDB_PLUGIN_MATURITY_GAMMA it should print "gamma", not "rc".

And for MariaDB_PLUGIN_MATURITY_STABLE it should not print anything (not "stable").

In your tests try to add a test for mysqld --version, for @@version, and for mysql \s