Now issues for me installing https://store.gx.me/mods/a7t0tm/official-cyberpunk-2077/ in Opera GX 112.0.5197.104 64-bit on Windows 11 23H2.
Maybe the download was just corrupted.
If it keeps failing, download the mod by right-clicking on this link and choosing "save linked content as". Then, once downloaded (resume/retry over and over if necessary until the download finishes), hit ctrl + o in Opera and point it to the crx file.