I am reaching out to request that the ShareX installers and/or the files be digitally signed. I am requesting this as my department is exploring the possibility of using this software in an enterprise setting (as an alternative replacement to similar software such as SnagIt and Greenshot) and our security team requires applications to be digitally signed (from a verifiable trust chain) so that it can be validated and recognized as pre-approved software.
I did review prior issues (#578, #1463) opened concerning this and it looks like both issues have been closed and current versions do not contain a digital signature. A list of Certificate Authorities is available here: https://en.wikipedia.org/wiki/Certificate_authority
The cheapest I have been able to find that would be sufficient for this purpose is Certum (which is $25 Euros or Approximately $27.11 USD per year).
I was also able to find this relevant blog post that details how to digitally sign software using Certum as an example: https://blog.aluxian.com/free-code-signing-certificate-for-open-source-software-d836270823a7
NOTE: I am not affiliated with any of the companies mentioned above.
One additional alternative that appears to be free / open-source (Not sure if it would serve the purpose): https://www.vchain.us/ & https://www.codenotary.io/
Looking for a certificate similar to the one pictured below (SHA-256 preferred):

Getting a Certum certificate shows your legal name as the certificate common name, which @Jaex understandably does not want to do. Other options like purchasing a full certificate where you could customize the common name are very expensive for an open source project (~200/year)
The alternatives you listed don't go back to any of the Windows-default root CAs
There really is no cheap open source cert, as a dev myself i just think it's way too expensive just to sign an app and have it somewhat trusted by windows.
I tried ascertia.com with a trial code cert (originally $17) but even those are not in the windows default trusted certs so it will still popup with the windows defender warning.
Cheapest is comodo $75 and highest is $664 a year good lord https://www.digicert.com/code-signing/
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Getting a Certum certificate shows your legal name as the certificate common name, which @Jaex understandably does not want to do. Other options like purchasing a full certificate where you could customize the common name are very expensive for an open source project (~200/year)