that is showing a warning - warnings are not errors, and they rarely indicate a problem - they can usually be ignored

if the program is not demonstrating unexpected behavior, then there is nothing interesting for a bug report - if anything were to be interesting for any bug report, what is most interesting, is to always show the commands that you typed, which produced the error messages - even if this were a bug, you have not provided enough information for anyone else to confirm it - if a bug can not be confirmed, then it can never be fixed

please use the bug report template, when reporting bugs - the first suggestion is especially important (pacman -Syyuu base your-freedom)

for example, based on the information you have given, this bug report should look like this:

• steps to reproduce:
  

  pacman -Syyuu base your-freedom                   # try me first (systemd) - did you do this?
  pacman -Syyuu base your-freedom your-initfreedom  # try me first (openrc)  - or this?
  pacman -S tor
  tor                                               # is this the command you typed?
                                                    # if not, which command produced the warning?
                                                    # was it run as a systemd or openrc service?

• expected result:
  i expected tor not to show me any warning messages

• actual result:
  tor showed me this warning message:
  Starting tor ...Feb 17 19:49:03.256 [warn] Tor was compiled with zstd 1.5.0, but is running with zstd 1.5.1.

given that clear bug report, it would be simple to answer - something like:

this is not a bug; because the "actual result" (warning messages) are normal behaviour - warnings are usually harmless, and only very rarely would they indicate a problem (or anything of interest) to the user - they are mainly interesting as hints to the programmers and maintainers of that software

if you can offer a more accurate "steps to reproduce", someone could try it on arch - tor and zstd are both arch packages

arch users get the same warning - if the program is behaving normally, this is probably not-a-bug then

Feb 19 03:18:21.556 [warn] Tor was compiled with zstd 1.5.0, but is running with zstd 1.5.2. For safety, we'll avoid using advanced zstd functionality.