Consider using Microsoft Defender Antivirus, which is built into Windows and provides real-time antivirus and malware protection without requiring additional security software. It is generally a good fit for the Surface Go because it has relatively low system overhead compared with many third-party antivirus products.
Keep Microsoft Defender Antivirus enabled and make sure Windows Security and Windows Update are kept up to date. You can verify this under Settings > Update & Security > Windows Security > Virus & threat protection. Defender also works with Microsoft Defender SmartScreen to help protect against malicious websites, downloads, and applications.
I would avoid installing a third-party antivirus unless you have a specific requirement for one. On a first-generation Surface Go, additional antivirus software can consume valuable CPU, memory, and storage resources and may also introduce drivers or other components that can interfere with Windows operations.
If this is related to the in-place upgrade problem you mentioned, Defender is also preferable during troubleshooting because you can temporarily disable its real-time protection without introducing a third-party antivirus driver or security suite that could interfere with the upgrade.
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hth
Marcin