Linux and its software is constantly under development and the community seems to really be making an effort to ensure that programs work exactly as expected. I often notice little things like glitches or program crashes and I am able to replicate them and I think I should probably submit a bug report or something. Since I am not a dev I have no idea how to do this or where to start. How do I know if its my issue or the programs issue?
For example, Thunderbird 115.1.0 is crashing when I open a specific email. I will put the steps I took to debug it in the comments.
Generally each software will have its own avenue of bug reporting. Mozilla probably has their own bug tracker for Thunderbird, you should post there. Smaller projects might have a GitHub issues tab.
Reproducibility is much more valuable than logs, but logs are good too. You should include the software version, your OS version, and other details about your system that are relevant to the specific problem. For yours, you might want to include a sanitized copy of the email.