I have the same issue. The message I am receiving is:

Opera installer 71.0.3770.228.0

Fatal error upon loading installer executable:

In line 199:The system cannot find the file specified., In line 273:The operation completed successfully., In line 304:The operation completed successfully., In line 199:The system cannot find the file specified., In line 273:The operation completed successfully., In line 308:The operation completed successfully., In line 178:The specified procedure could not be found.,

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